Ka-Ran and Nam-Joon were classmates in elementary school. Ka-Ran is a tomboy who prefers trousers to skirts, and loves taekwondo more than her piano lessons. Nam-Joon on the other hand is Mr. Perfect and Wonderful who's got the good looks and the fine brain. No doubt, he is the most popular guy among the girls. One day, Ka-Ran witnesses the scene where Nam-Joon gives away the sweet bun which he got from Ka-Ran's friend to another girl. Ka-Ran throws herself at Nam-Joon and beats him up. From that on, their "nightmare(?)" begins...
Hahn, Ga-Ran (acted by Choi Kang-Hee)
She's the only daughter but she's not the common spoiled-little-brat only child. She's rather more of a maid who's always ready to give and serve than a princess who's ready to be served. She prefers trousers to skirts. She's satisfied with what she's got and never envious of what other people have. She's bright, active, and optimistic. She's very naughty boasting a great amount of energy. This makes her very popular among her students. To her, loyalty and integrity always come first. She always knows what is right or wrong and where to go but when it comes to love, she's totally lost.
Ahn, Nam-Joon (acted by Park Kwang-Hyun)
He was the youngest man to pass the bar exam and currently working as a lawyer for a construction company. He's got the good physical looks and a brain, in other words he's the "Mr. Perfect". Outwardly, he seems frigid and lazy but he's a large-hearted man. He just doesn't know how to well express himself. He's full of competitive spirit and has never lost a single competition. He's satisfied only when he says all he wants to say even in a simple quarrel. But likewise, no matter what he only pursues one, be it love or work. Love in particular is really something to him. To him, love only exists in the form of one girl, Hae-Jan.
Yoo, Kwan-Ha (acted by Jeong Chan)
He's the 33-year-old president of a construction company where Nam-Joon works. He's taciturn and cilly with a charisma that overwhelmes and brings people together. With a positive drive, he always makes whatever he thinks happen. Almost all the things have been going the way he wanted so he's always full of confidence. Girls had never been part of his interests. But even this guy feels himself changing when he accidentally encounters Ka-Ran. Ka-Ran doesn't seem like the ordinary girls he used to meet. She doesn't even seem to be scared of the hooligans. He slowlys feels himself falling for Ka-Ran but somehow she doesn't seem to open up her heart to him.
Hong, Hae-Jan (acted by Jeong So-Yeong)
She was Ka-Ran's elementary school classmate. She's the youngest daughter of a renowned family in the southern province of Korea. She really does represent the word "princess-like" itself. She's always composed, cultured and of course with a perfectly pretty face and figure. Unlike Ka-Ran, she's used to being served and nicely treated by other people, especially the men. She in fact enjoys getting this kind of attention from men and has always been the center of men's attention ever since she was little. She's the kind of girl with every quality that a girl would ever want and this naturally makes other girls very jealous.
Ka Ran, an elementary school teacher, breaks into tears along with her students as they say farewell to Young Min, who is to be transferred to another school. Watching Ka Ran weep, teachers say that Ka Ran looks more like a student than a teacher. Nam Joon, a lawyer, goes to his hometown Jun Joo where his sister Nam Hee, an elementary school teacher, and her husband, Jung Hoon, are living. Nam Joon visits Jung Hoon's workplace to look for a job, but encounters organized criminals, which leaves a bad impression of the company.
Ka Ran plans to buy a wedding gift for her friend, but as something urgent happens, she asks her friend Sun Hee, also a teacher, a favor. Later, they get together and accidentally see the back of Nam Joon. Ka Ran follows the guy wondering if he's the one she has been looking for, but loses him. Depressed, Ka Ran and Sun Hee drink and got high.
Nam Joon, who visits school to do a favor for his sister Nam Hee, encounters Ka Ran and Sun Hee for the first time. Thanks to Sun Hee's brilliant memory, Ka Ran realizes that Nam Joon is the 'sweet bun' with whom she was on bad terms in the past, and thus, she is very short with him. Nam Joon also soon realizes that Ka Ran is the one he has a bad memory with.
On the way to a video lending shop, Nam Joon fails to recognize a bicycle coming around the corner, and collides with it. Ka Ran is the rider, and the two bicker with each other again. The next day, Nam Hee, annoyed by Nam Joon's all-day-long sleep, drags him forcefully to a swimming pool. Nam Joon sees Ka Ran there by chance...
After wrangling with Nam Joon, Ka Ran suddenly becomes gloomy, and gets drunk after drinking alone. Under the influence, she plays a trick on Sun Hee through phone, and is amused by Sun Hee's credulity. However, when Ka Ran returns home, she gets depressed again and sheds tears. As they leave home, Ka Ran and Sun Hee get into a fender bender. Evil-looking offenders blame Ka Ran and Sun Hee for the accident, but Ka Ran strongly opposes, saying "you are the ones responsible for the accident." On the brink of a quarrel, Kwan Ha, seemingly the boss, shows up and apologizes. Meanwhile, Nam Joon is disappointed as his friend Duk Jin, who runs a photo studio, fails to get him the phone number of Hye Jan, Nam Joon's first love.
Ka Ran and Sun Hee go to a friend's wedding, but tries to get out of the place as soon as possible because the bridegroom's friends are all evil-looking. However, they are forced to attend the wedding reception, and Ka Ran suggests playing a game to get herself out of the place quickly. Before long, Kwan Ha appears, and Ka Ran, who has been leading the game, loses control to Kwan Ha. Kwan Ha shows his interest in Ka Ran.
Depressed by his failed attempt to get Hye Jan's number, Nam Joon hums the number song that Ka Ran used to sing in the playground. Passing by the place, Ka Ran is curious who's singing her favorite song, and finds Nam Joon. Her face hardens. Ka Ran tells him nut to sing that song, but he ignores and continues singing...
Kwan Ha, who has had an official meeting with Nam Joon, cancels a dinner appointment and goes to Ka Ran. However, Ka Ran, quite uneasy about Kwan Ha's appearance, almost introduces him to Sun Hee. Nam Joon feels sad as Nam Hee says there is no news from Hye Jan lately, and goes to his room, staring at Hye Jan's picture.
The next day, Ka Ran and Nam Hee are surprised to hear that Hye Jan is working as a temporary teacher. Nam Hee tells Nam Joon, who has attended his office for the first time, that Hye Jan is at school, and Nam Joon rushes to the school. While Nam Joon is impressed to see Hye Jan, she seems rather a bit troubled. Ka Ran goes see her student Seung Min, working in a night club, to make him return to school. However, Seung Min doesn't listen, making Ka Ran anxious. Ki Dong, right next to them, beats him. Ka Ran is stunned, and tries to have a talk with Seung Min, but things get worse, making her more depressed. Meanwhile, Ka Ran comes across Kwan Ha and Nam Joon who have come to the night club for a gathering. At school, Ka Ran feels bad when she realizes that her student was put at a disadvantage by Hye Jan after Ka Ran's student and Hye Jan's student fought. Ka Ran goes to Hye Jan to talk about it, but feels even worse. The two teachers unwillingly accept the assistant principal's proposal to work together on the library guideline program. Though Nam Joon goes to the school to see Hye Jan after successfully obtaining her phone number, he's dumbfounded by her shocking remarks...
Nam Joon is shocked by Hye Jan's remark that she's getting married next month. He vacantly says "congratulations" and leaves the school. Ka Ran tells him to cheer up, but he feels worse. Ka Ran is irritated by Nam Joon's response despite her goodwill, and as she sees Sun Hee eating sweet buns, she snatches them away.
Disturbed Nam Joon drinks a lot, sometimes losing consciousness or wandering in the rain. Unlike in the past, he devotes himself to work, leaving many others wondering. Nam Hee, unaware of Nam Joon's anguish, asks Hye Han to soothe him, saying that he gets easily exhausted, but Hye Jan has no idea what to do.
Nam Joon, even busy at home organizing files, is shocked to see Hye Jan enter his room. He feels bitter when she says that she wants to be friends with him. As he leaves home to take her home, he is uneasy to see Kwan Ha and Ka Ran just in front of them. Ka Ran is also feeling uncomfortable with Nam Joon's appearance.
Nam Hee tells Nam Joon to go see the principal before vacation starts, so he visits the school with his friend Duk Jin. Since Ka Ran is having a chat with the principal, Nam Joon tries to avoid confronting her. Nam Joon leaves to have a dinner with the principal, and Ka Ran meets Seung Min who has turned to a student from a night club waiter. Ka Ran, listening to Seung Min's story, blusters herself into anger when he mentions 'Kwan Ha'...
While bickering with Kwan Ha, Ka Ran, surprised, breaks into tears when Shin Hyuk calls her. A moment later, Shin Hyuk tells Ka Ran that he has come to the parish of Jun Joo as a priest and that he missed her a lot. Ka Ran, who has remained firm and strong, can't help but weep. Ka Ran cries once again when she sneaks into the church and peeks at Shin Hyuk. Nam Joon is on one hand surprised at Shin Hyuk's showup, and feels pity for Ka Ran on the other hand. Nam Joon can't cover up his sadness as he talks with Ka Ran, Duk Jin, and Sun Hee about Hye Jan's wedding and Shin Hyuk's showup at a cafe. Ka Ran, just like what Sun Hee recommended, touchingly sings 'Under the same sky' on the stage, expressing her love.
Nam Jun takes Ka Ran to a pub to have another drink. They say that they never knew they would drink by themselves, but they become good friends again as they get high, toasting. However, the next day, as they get sober, they have almost no memory of the previous day. Ka Ran visits Kwan Ha's company to deal with Seung Min's problems, but she and Nam Joon both feel awkward...
When Nam Joon and Ka Ran are about to leave for lunch, Hye Jan joins them, and the three go out together. They can't hide their uneasiness, and Hye Jan tells Nam Joon to tell Nam Hee about their breakup. Ka Ran is enraged by his selfishness, and she leaves the restaurant carrying Nam Joon's and her leftover food.
Kwan Ha suggests that he and Nam Joon play fair to win Ka Ran, but Nam Joon rejects his suggestion, saying that he himself is a dirty player. Nam Joon feels sorry for Ka Ran since he thinks that he hurt her by pretending as if nothing happened between him and Hye Jan, so he goes to Ka Ran's place. Kwan Ha suddenly appears before Ka Ran, who is planning to go fishing with her students. Ka Ran, briefly perplexed, enjoys a great time fishing with Kwan Ha and the kids. They are startled when a kid falls into a river, but Kwan Ha saves the child, relieving everyone.
When Nam Hee belatedly learns that Nam Joon and Hye Jan broke up, she is saddened by the fact that no one has told her about it. Nam Joon suggests dining out to please Nam Hee, and the family heads for hotel. However, Nam Joon comes across Hye Jan and a man there who seems like Hye Jan's boyfriend.
Nam Joon asks Ka Ran to date him for a hundred days, telling her that he has more feelings for her than before. Ka Ran, perplexed, tells him not to joke around, but Nam Joon is serious. Nam Joon is surprised when he finds a letter that Ka Ran has kept. Having secretly watched him, Kwan Ha is cold toward Nam Joon. Nam Joon and Kwan Ha get tense over Ka Ran. Kwan Ha feels bitter when Nam Joon says that there has been no Kwan Ha in Ka Ran's memory of last 20 years. Ka Ran is at a loss when she hears from Nam Joon that the letter she has kept for so long was written by Nam Joon. Ka Ran, out of her mind, goes to the church and is startled when she meets Shin Hyuk and Kwan Ha there. Shin Hyuk and Kwan Ha turn out to be close friends from university days. Kwan Ha tells Ka Ran that Shin Hyuk had worried about himself a lot before he decided to become a priest, and advises her to leave Shin Hyuk alone and be comfortable with that. Ka Ran weeps when she thinks that Shin Hyuk must have been hurt by her. Nam Joon refuses to accept Nam Hee's proposal that he go on a blind date, and goes to where Ka Ran is receiving Korean music lessons. Nam Joon comes across Hye Jan there, and he tells her that he's dating Ka Ran...
Nam Joon says he's dating Ka Ran when he comes across Hye Jan, and Ka Ran and Hye Jan are stunned. Ka Ran asks Nam Joon why he likes her, and Nam Joon says that though Hye Jan comes to his mind when he wakes up at night, he believes that he can love Ka Ran since he's always happy when he's with Ka Ran. Kwan Ha goes to Shin Hyuk and tells him about his special feelings for Ka Ran. He promises to keep his distance from her, saying that he misunderstood her though he thought he knew Ka Ran well. Kwan Ha, when he sees Ka Ran, tells her that though he has stayed where Ka Ran can see him easily so far, he will walk behind her from now on.
Ka Ran meets with Nam Joon when she goes to the hospital where the principal's wife is. The principal says that the two make a good couple, and Ka Ran, embarrassed, leaves. In Ka Ran's absence, Nam Joon tells the principal that as far as he knows, Ka Ran is a caring person, but that she's always grumbling to him. Hye Jan gives Ka Ran her wedding invitation. Hye Jan also tells her, stunned, to give Nam Joon the invitation. However, Ka Ran says that Hye Jan'd better give it to Nam Joon directly. Hye Jan meets with Nam Joon, who's feeling uncomfortable about her, and asks him to congratulate her on the wedding. Nam Joon is shocked and disappears...
Nam Hee, perplexed by Nam Joon's disappearance, presses Hye Jan to disclose who he likes, and Ka Ran and Hye Jan feel uncomfortable about it. Nam Joon takes Hye Jan's photo out of his purse, but puts it again after some deliberation. A moment later, Nam Joon goes to Ka Ran and tells her why he went away. The two have a meal together and sing songs. Nam Joon asks Ka Ran out once again, but Ka Ran says that she will have to think about it.
Before long, Nam Joon goes to Ka Ran urging her to go out with him. Ka Ran, at a loss, helplessly accepts his request, and the two have a great time in agame room acting like children. When Nam Joon tells Ka Ran the ways to forget about Shin Hyuk, she decides to go see Shin Hyuk. However, when Shin Hyuk averts his eyes from Ka Ran, she feels depressed and goes to Kwan Ha. When she learns from Kwan Ha that Shin Hyuk did indeed suffer because of her, she feels all the more bitter.
After arguing over the phone, Hye Jan feels depressed. When teachers talk about her wedding invitation, she wants to avoid them. Later on, Hye Jan meets Nam Joon and blames him for making her embarrassed by his disappearance. Ka Ran, who happens to pass by and overhear their conversation, gets angry at Hye Jan for blaming him. Resolute, KaRan moves toward the two and makes a surprise remark...
Ka Ran goes to Nam Joon and Hye Jan, who seem to be blaming him. Ka Ran announces that she will go out with Nam Joon from now on. Though surprised by Ka Ran's behavior, Nam Joon thinks that that's what he has wanted, and buys Ka Ran sweet buns to say that she should get rid of her past memories. He also frequently calls Ka Ran. Ka Ran feels uncomfortable with this new behavior of Nam Joon. Nam Joon begs Ka Ran to make time for him and says that he has bought movie tickets in advance. However, when Sun Hee suggests dinner, Ka Ran ignores Nam Joon's request and goes to dinner. She sees Sun Hee and Kwan Ha there, and the three have a great time singing. Nam Joon, left alone, has dinner with Jung Hoon and Ki Dong and they talk about Ka Ran and Sun Hee. Nam Joon gets mad when he sees Ka Ran getting out of Kwan Ha's car. However, Nam Joon pretends he hasn’t seen anything, and calls Ka Ran. When she abruptly hangs up, he feels confused. The next day, Ka Ran, who has felt sorry for Nam Joon, is startled to receive a phone call from him, something that she has long awaited.
Ka Ran is embarrassed when Hye Jan tells Nam Hee that Nam Joon's seeing someone, and she doesn't know what to do when Nam Joon, having a chat with Kwan Ha at a pub, invites her there. When Ka Ran and Nam Joon hear the principal's remarks about Hye Jan, the two are shcoked. Sun Hee is at a loss when she learns from Ki Dong that Nam Joon and Ka Ran are going out...
Ka Ran and Nam Joon are surprised to hear from the principal about Hye Jan's cancelled wedding. During a chat with Nam Joon, Ka Ran says that now that Hye Jan is not getting married, her relationship with him should end. He flatly says that the relationship should go on since it has nothing to do with Hye Jan's wedding.
As Ka Ran leaves her house for school the next day, Nam Joon appears before her and asks her if she is free that night. At school, many teachers soothe Hye Jan, but she can't hide her pain.
Hye Jan goes to Nam Joon and explains why she broke up with her boyfriend. Nam Joon, slowly moved by her words, sides with her. While reading a book, Ka Ran gets a phone call from Kwan Ha, and indirectly asks him if he's free. He postpones his important appointment with a bank, and runs to Ka Ran. On the way home, Nam Joon and Hye Jan witness Ka Ran getting out of Kwan Ha's car. Nam Joon is not pleased to see this, but Hye Jan soothes him. Sun Hee invites Ka Ran, Nam Joon and Ki Dong over for a meal. Sun Hee, when left alone with Ka Ran, tells her to be nice to him, and weeps...
When Sun Hee disappears, Ka Ran tells Nam Joon that Sun Hee has learned that Ka Ran and Nam Joon are dating. Ka Ran also adds that Sun Hee frequently meets with Duk Jin these days, and Ka Ran and Nam Joon rush immediately to Duk Jin's photo studio. However, Sun Hee is not there, and at home, Ka Ran weeps, holding Sun Hee's pillow and wishing for her quick return.
Sun Hee, heading for the photo studio, spots Ka Ran and Nam Joon, and calls Kwan Ha. Sun Hee goes to a sauna with Kwan Ha, and she tells him to excuse her for calling him. She goes into a sauna room, and at that moment, Kwan Ha calls Ka Ran and tells her that Sun Hee is with him. Ka Ran finds Sun Hee with the help of Kwan Ha, and tells her that she is not dating Nam Joon any more. Sun Hee's surprised.
Sun Hee meets with Nam Joon, and urges him to go out with Ka Ran since she doesn't love him any more. Nam Joon tries to ask Ka Ran out, saying that it's the only way to prevent Sun Hee's disappearance. But Ka Ran gets angry. Ki Dong asks Sun Hee out, but is treated coldly by her. Nam Joon, set to go to Seoul to visit the family of a late professor, tells Ka Ran to see him in three days and not to miss him so much. Ka Ran is swayed when she sees Shin Hyuk presiding over the Mass, but she gets help from Kwan Ha. On the third day since Nam Joon left, he tells Ka Ran, who is busy preparing for an event, his arrival time, and asks her to come out to greet him...
Ka Ran is at the station to greet Nam Joon and gets embarrassed when she sees Nam Hee by chance. To make matters worse, when Nam Hee asks them if they are dating each other, their answers differ, with Nam Joon saying "yes" and Ka Ran "no." Nam Hee scolds Nam Joon for falling for Ka Ran, and Ka Ran is hurt. Nam Joon angrily declares that he will date Ka Ran no matter what Nam Hee says. Nam Hee asks Jung Hoon to separate Ka Ran and Nam Joon, but Jung Hoon ends up siding with Nam Joon when he goes to Nam Joon to persuade him. Nam Joon asks Ka Ran if she's angry about Nam Hee's behavior, but Ka Ran pretends as if she hasn’t been hurt by Nam Hee. At this moment, Nam Joon takes away Ka Ran's bicycle, and rides it to work. Kwan Ha feels uncomfortable hearing the story about Ka Ran and Nam Joon. Determined, Kwan Ha sends a text message to Ka Ran saying that he wants to go see a performance with her, and the two go to the classical music institute. Though Kwan Ha wants to have a meal with Ka Ran after the performance, Ka Ran goes to meet Nam Joon after getting several calls from him. However, Ka Ran unhappily returns home after she sees Nam Joon next to Hye Jan where they were supposed to meet. The next day, when Hye Jan tells Ka Ran that Nam Joon waited for Ka Ran for a long time, Ka Ran feels sorry for him. Nam Joon also feels sorry for Ka Ran and worries that Ka Ran may have seen him with Hye Jan. In the evening, Nam Joon takes Ka Ran to a shabby restaurant and the two have a good time. Kwan Ha and Shin Hyuk appear before them...
While they’re having a great time at the restaurant, Ka Ran and Nam Joon encounter Shin Hyuk and Kwan Ha. The four feel awkward. Shin Hyuk asks Ka Ran if they can join them, but Ka Ran, bewildered, rushes to leave. Kwan Ha later tells Ka Ran that he was disappointed that she didn't care about him. The next day, on the way to work, Ka Ran is surprised to see Nam Joon in front of her house, prepared to take her to work. She goes to work with him. As she witnesses Nam Hee and Jung Hoon in the distance, Ka Ran grumbles with her head lowered, but she feels better after eating the kimbob that Nam Joon gave her. Nam Joon goes to work after taking Ka Ran to the school, and tells Kwan Ha that if he wants to meet Ka Ran from now on, he has to adjust both Ka Ran's and Nam Joon's schedule. This gets on Kwan Ha's nerves. Nam Hee asks Ka Ran if Mr. Lee, a newcomer to the school, would make a good boyfriend, and says that if Ka Ran is interested, she can introduce him to her, which greatly disturbs Ka Ran. Ka Ran falls asleep in Nam Joon's car while he's taking her home. Nam Joon pushes her seat downward to let her have a good sleep, but at this moment she wakes up, and misunderstands his intention. In the meantime, Ki Dong brings Sun Hee a bowl of gruel to try and woo her, but she doesn't even care about him...
Nam Joon follows Ka Ran and kisses her. Surprised, Ka Ran pushes him away. Sun Hee leaves Duk Jin because of Ki Dong's appearance, and Ki Dong suddenly kisses Sun Hee's cheek. Sun Hee tries to forget what happened by washing her cheek, and Ka Ran also tries to forget the kiss by washing her lips. Ka Ran and Sun Hee, unable to sleep, have some drinks. Sun Hee learns that Ka Ran and Nam Joon kissed because of Nam Joon's phone call.
Still a little drunk, Ka Ran heads towards Baekyangsa to prepare for class. Sun Hee calls Nam Joon to tell him about Ka Ran's whereabouts, and he quickly goes to the Junjoo station. He spots Ka Ran, dozing off in a bench, carries her on his back into a train, and sits next to her. He is pleased when an old woman sitting in front of them calls them a newly-wed couple. While they’re waiting for Ka Ran in front of the house, Sun Hee tells Kwan Ha that she made Nam Joon stay with her.
Nam Joon and Ka Ran are in the Baekyangsa. Ka Ran takes pictures of Daewoongjun and others for class. When Nam Joon insists she take a picture with him, she grudgingly accepts. Nam Joon suddenly hugs Ka Ran and kisses her hand, trying to get closer. Ka Ran feels her heart pound. In the evening, Ka Ran and Nam Joon have dinner. At that moment, Nam Hee breaks in and Ka Ran, shocked, hides under the chair. She is soon caught. Nam Hee tells Nam Joon not to date Ka Ran, and indirectly tries to make Ka Ran part with Nam Joon by telling Ka Ran that Kwan Ha is more competent than Nam Joon. Kwan Ha makes a confession to Shin Hyuk, and drops a bombshell before Ka Ran and Nam Joon....
Kwan Ha makes a confession at a church that he will be honest with his feelings frm now on for the sake of the person he loves. He also adds that his friend has taken the most valuable person away from him. Shin Hyuk, who has been listening to Kwan Ha's confession, advises him, not as a friend but as a priest, to be nice to the person he loves. Nam Joon asks Ka Ran to go with him to the library to prepare for a trial. Nam Joon eagerly looks for data he needs in the library, and Ka Ran busily reads books, including Kim Yong Taek's anthology. At this moment Nam Joon holds Ka Ran's hand, and she is surprised. Nam Joon smiles contentedly, thinking it's the happiest moment in his life.
Ka Ran is responsible for the extension work on the school building. Nam Hee tells Ka Ran that if Ka Ran gets help from Mr. Yoo, it would be a good chance for her to get closer to him. Ka Ran is sad to hear that. Ka Ran meets with Kwan Ha to tell him about the school's situation. Kwan Ha is happy to hear about it and discusses library construction with Ka Ran.
When Nam Joon learns about it, he tells Ka Ran not to meet Kwan Ha. Ka Ran says thatshe can't do that because of the school situation. Nam Joon is upset when he witnesses Kwan Ha trying to help Ka Ran's work. Nam Joon worries about it at home alone, and finally...
Kwan Ha declares before Nam Joon that he will go out with Ka Ran on his own terms from now on. Nam Joon is surprised to hear that, but he remains firm, saying that he will get ready for everything since Ka Ran is his friend. Ka Ran tells Sun Hee that though she thinks of Kwan Ha as just a friend, Nam Joon won’t believe her, and that irritates her very much. However, Sun Hee surprises Ka Ran by saying that she will not side with anybody from now on.
Nam Joon feels somewhat embarrassed when he sees Hye Jan in his house. She is about to leave, and he takes her home. Nam Joon is surprised to see Ka Ran unexpectedly before the house. When Ka Ran sulks after witnessing Nam Joon and Hye Jan next to each other, Nam Joon follows Ka Ran without caring about Hye Jan. Ka Ran and Nam Joon have a long chat, and he kisses her on her cheek, reaffirming their love. Ka Ran gets gloomy when the assistant principal tells her that she would make a good match for Kwan Ha. Nam Joon also gets upset when Jung Hoon tells him that Ka Ran and Kwan Ha make a good match. Nam Joon eventually goes to the school where Ka Ran is teaching, and he introduces Ka Ran as his girlfriend to students.
Nam Hee, pressured by Nam Joon, finally invites Ka Ran to her house. Nam Hee secretly tells Ka Ran that it would be better if she went out with Kwan Ha, and Ka Ran is upset. Ka Ran tells Sun Hee about it to relieve her sadness, and Sun Hee says that Kwan Ha fits Ka Ran better than Nam Joon. The next day, Ka Ran meets with Kwan Ha because of the construction of the library, and the two have a great time. After witnessing the two hanging around together, Nam Joon makes a critical decision.
Nam Joon tells Ka Ran that he wants to give up going out with her since it's difficult, and goes on his way. Ka Ran says, "If you leave now, it's the end." She waits for Nam Joon, but he doesn’t return. She also leaves. However, before long, the two miss each other, and Nam Joon, screwing up his courage, calls her and asks her to meet him before the house. But the two fail to meet since Ka Ran waits for him before his house, and Nam Joon before her house.
Ka Ran catches a cold because of bad weather, and when Kwan Ha learns by chance that Ka Ran is sick, he takes her to the hospital that his uncle runs. Thanks to him, she returns home in a better condition. She encounters Nam Joon, who has already been waiting for her. Nam Joon feels sorry for Ka Ran when he learns from Sun Hee that Ka Ran is sick and that Nam Hee is very serious about Ka Ran. He hugs Ka Ran as soon as he sees her.
Nam Joon returns home, and when he sees Hye Jan right next to Nam Hee, he fails to talk with Nam Hee about Ka Ran. Nam Joon takes Hye Jan home, and feels somewhat awkward that Hye Jan so easily approaches him. Kwan Ha visits Ka Ran's place for a while, and tells Sun Hee that he is happy to be able to take care of the ailing Ka Ran.
Hye Jan asks Ka Ran how much she knows about Nam Joon, and also adds that she will try once again to go out with him since he is too good for Ka Ran. Ka Ran is speechless. She can't even continue her class, and fails to give a clear answer when Nam Joon suggests that she spend time with him. Ka Ran, now left alone, carefully thinks about her relationship with Nam Joon. Ka Ran goes to the movies with Nam Joon. Ka Ran wants to watch a horror movie and eat squid, but he doesn't listen.
The two leave the theater because of that disagreement, and end up in a restaurant. However, once again, they disagree on what to eat, and finally return home instead of enjoying a lovely date.
Ka Ran goes to an outdoor pub with Kwan Ha when he comes to see her. She tells him that she is sorry that she has already drawn a line, and to please not look for her from now on. Having been advised by Kwan Ha, Sun Hee calls Ki Dong, worried about him
Nam Joon, having calmed himself down, looks for Ka Ran, and asks her to go to the movies with him saying that he will behave from now on. Ka Ran, feeling a bit better, waits for Nam Joon in the theater, but he breaks his promise since he fails to shake Hye Jan off.
Ka Ran feels uneasy when Kwan Ha suddenly asks her out and gives her a ring. Ka Ran asks him not to do so, saying that there is Nam Joon to think about. Kwan Ha asks her if she loves Nam Joon. Hesitating for a moment, Ka Ran tells him that it will be really difficult for her to meet him again, and leaves.
Nam Joon, not knowing about it, apologizes to Ka Ran for breaking his promise because of Hye Jan. He adds that he will love only Ka Ran no matter what situation she is in. Sun Hee, concerned about Ki Dong after hearing that he is not eating or drinking anything, meets with Ki Dong with the help of Ka Ran.
The next day, Ka Ran goes to Nam Joon's house, and waits for him. Nam Joon, feeling strange about her actions, takes her to the school on a bicycle. Ka Ran tries to get closer to Nam Hee, but she is still upset that she can't help getting nervous before her.
A while later, Ka Ran suggests to Nam Joon that they list 20 things that they like and another 20 that they hate. Nam Joon is at a loss, but agrees. The two exchange what they wrote, and get to know something that they never knew before. However, Ka Ran recalls the days when she went out with Shin Hyuk, and feels something is missing in her relationship with Nam Joon. Later, she visits Shin Hyuk, and finally drops a bombshell before Nam Joon.
Nam Joon tells Shin Hyuk that though he tried to make Ka Ran’s life happier, she said that there was only one person who could do so. Shin Hyuk tells Nam Joon that it was the very first time that she told him about anyone else, and also advises him to make his own life happier before he tries to make her life happy. Nam Joon, impressed, goes to Ka Ran, and tells her that he will not bother her anymore.
Ka Ran is absorbed in thoughts when the principal tells her that she’d better take Nam Joon as he is rather than try to change him. Ka Ran goes to a noodle restaurant with Shin Hyuk. He tells her that she should stop comparing him to Nam Joon and should try to see things as they are. Ka Ran is disappointed to hear that. Shin Hyuk, who has returned to the church, prays that she will make wise decisions.
Nam Joon returns home, and sends an e-mail to Ka Ran, saying that he did things that Ka Ran liked, and though he can’t become Shin Hyuk, he will continue to express his feelings. Ka Ran is once again absorbed in thought.
The next day, Hye Jan meets with Nam Joon, and asks him out seriously. However, he surprises her by saying that he still likes Ka Ran. Ka Ran, anxious, roams around, and when she comes across Nam Joon accidentally wherever she goes, she feels guilty. Sun Hee informs Nam Joon of Ka Ran’s upcoming birthday, and goes shopping to buy Ka Ran’s birthday gift with Lee. Nam Joon does not know what to do about Ka Ran’s birthday.
Nam Joon, who now knows when Ka Ran’s birthday is, wholeheartedly prepares for a birthday party for her. He plans to leave before Ka Ran comes. Impressed by Nam Joon’s efforts to throw a party for her, Ka Ran invites him to the party. Nam Joon jokingly asks Ka Ran if she wished for a perfect love as her birthday wish. Ka Ran says that she still likes Shin Hyuk. Nam Joon says that he already knows that, and so he will find a place somewhere near her so that she may like him too.
Nam Hee offers Nam Joon a drink, and tells him not to blame her too much for the breakup with Ka Ran. However, he makes a surprising remark that he is going out with Ka Ran again. Nam Joon says that while he always had to be gentle and nice to Hye Jan, he was always just himself before Ka Ran, and that’s why he likes Ka Ran. Nam Joon and Ka Ran go to the movies together. They disagree about which movie to see, so Ka Ran suggests that the person who wins rock-paper-scissors gets to decide. Nam Joon agrees. Ka Ran wins the game, and she chooses a horror movie. Nam Joon looks scared, and Ka Ran can’t help laughing. She gets a phone call from Kwan Ha, but Nam Joon takes the cell phone from her and answers it. He meets with Kwan Ha. Kwan Ha expresses his romantic feelings for Ka Ran. Ka Ran feels pity for him. Nam Joon, aware that it’s been 100 days since he went out with Ka Ran, prepares some kind of an event.
Nam Joon shouts “I love you” though a microphone in the school studio to Ka Ran. Shocked, she tries to stop him, but he asks her to marry him through the microphone. The principal and other teachers, including Hye Jan, look at Ka Ran and Nam Joon out of curiosity. After returning home, Nam Joon calls Ka Ran, and sings her a song.The next day, Ka Ran, feeling pity for Hye Jan, asks Nam Joon to soothe her. He is surprised, but he does what Ka Ran asks. He meets with Hye Jan for a drink and they decide to leave each other completely. Nam Joon, drunk, looks for Ka Ran, and she takes him home. Sun Hee has a talk with Duk Jin, who has come to ask her out, and is embarrassed when Ki Dong calls him.Ka Ran wakes up early to take care of Nam Joon. Nam Joon, excited, runs to Ka Ran. She buys him a bowl of broth. Ka Ran, at school, feels bad when Hye Jan tells her that Ka Ran is just too good a person to be Nam Joon’s girlfriend. But she soon calms down. Ka Ran feels awkward when Nam Hee becomes nice to her. While Nam Joon is talking with Ka Ran on the phone, suggesting they buy special rings for each other, Kwan Ha tells him to get in his car so that they can go to the school together. Nam Joon, feeling a bit nervous, feels sorry for Kwan Ha when he leaves after Nam Joon took off from the car. Ka Ran and Nam Joon now have their rings and they are confident about their love.
Ka Ran calls Nam Joon by his name, and he is both surprised and thankful for that. Ka Ran, who has returned home, tells Sun Hee that Nam Joon got very happy when she called him by his name. Nam Joon brags about the rings he and Ka Ran have before Nam Hee and Jung Hoon. The next day, Nam Joon gives Ka Ran’s students sweet buns. However, the students don’t seem happy about it. When Kwan Ha gives them notebooks, they seem very happy. Kwan Ha leaves after finishing his work, land Ka Ran feels bitter when she sees him walking away
.Ka Ran learns from her father that Nam Joon has visited her house. Ka Ran is surprised and searches for Nam Joon in her pajamas. She is speechless when she learns that he has already sent wedding cards to other people.
Shin Hyuk meets with Kwan Ha, and tells him that he may leave for Choonchun. Surprised, Kwan Ha visits Keumkang to calm himself down. Having seen all this, Ki Dong asks Ka Ran to go out with Kwan Ha.
Ka Ran, pressured by Ki Dong, goes to where Kwan Ha is staying. Kwan Ha is surprised at Ka Ran’s sudden appearance, but he tells her that he has come to Keumkang to completely forget about Ka Ran. He says that he will not regret the days he had with Ka Ran. He takes a ring out of his pocket, and throws it into the river. Nam Joon feels sorry for Kwan Ha, thinking that though he has a lovely girlfriend like Ka Ran, Kwan Ha must be very hurt. Ka Ran says that Kwan Ha once told her that she gets prettier when she’s next to Nam Joon. But when she remembers the wedding invitations, she almost chokes him. Nam Joon suggests they get a bank account under both their names. He goes on to say that they’d better save money so that they can buy necessary things when they get married. She says that she wants to have the control of the bank account. They get a phone call from Ki Dong, and instead of going to a concert, they meet with Ki Dong, who is heartbroken because of Sun Hee.
It’s the New Year. Nam Joon, Ka Ran and Sun Hee celebrate New Year’s day with champagne. Nam Joon tells Sun Hee that he and Ka Ran will always side with Sun Hee no matter who she chooses as her boyfriend. Shin Hyuk gets ready to move to the Choonchun parish, and that surprises Ka Ran and Nam Joon.
Ka Ran gets sad when she realizes that Shin Hyuk has already left the church. Nam Joon, standing next to her, gives her a sweet kiss, and says that he will love her tomorrow more than today and the day after tomorrow more than tomorrow. Nam Joon says he is thankful for her being next to him whenever he’s depressed. Ka Ran also feels thankful for Nam Joon, who has helped her a lot.
The next day, she is surprised that Nam Joon and Nam Hee have come to her house at such an early hour. Ka Ran and Nam Hee go to the sauna together. Ka Ran is not only unfamiliar with the sauna but also uneasy about being next to Nam Hee. However, Nam Hee soothes her saying that she will help her. Ka Ran meets Kwan Ha and Nam Joon for lunch. Ka Ran hears Shin Hyuk’s news from Kwan Ha, and feels relieved.
Ki Dong tries to propose to Sun Hee by hiding a ring between heads of lettuce. Nam Joon, Ki Dong, Ka Ran, and Sun Hee enter the restaurant and start eating. Ka Ran accidentally finds a ring, and this discourages Ki Dong. Ki Dong gets all the more embarrassed when the ring does not fit Sun Hee’s finger.
On the way home, Nam Joon says that he wants to hear Ka Ran say “I love you.” She shyly makes a heart with her arms, and Nam Joon gets very happy. Ka Ran invites Nam Joon to her house, and asks him to marry her after pretending she’s making a test.