Plot(Wikipedia)
Lee Mong-ryong, son of a famous chief of police, is transferred from Seoul to a high school in Namwon, North Jeolla Province, because he is a trouble maker. He accidentally bumps into Sung Chun-hyang, shoots embarrassing photos of her and ends up swapping her cell phone with his. As a result, they are constantly in touch with each other and find out they attend the same school. Mong-ryong constantly bullies Chun-hyang and thanks to him, she becomes slightly sick. Feeling guilty, he visits her, only to mistakenly drink a whole bottle of wine, assuming it is juice. He immediately falls asleep on the only bed in the house, which consequently is the one Chun-Hyang is sleeping in. Thus, they spend the night with each other. Nothing sexual occurs, but thanks to their best friends, who know what happened and accidentally announce it on the school intercom, they are forced to marry each other in order to save their families' reputation, seeing as everyone at school assumes they have slept together. They eventually fall in love with each other, but Mong-Ryong's previous crush, Hong Chae-Rin, after rejecting him, then discovering his marriage, becomes jealous and tries to win him back. There is also the problem of Byun Hak-Do, an extremely successful talent agency director who falls in love with Chun-Hyang.
In order to help him get to college, Chun-Hyang helps him to his study so that he could be with Chae-Rin at Han-guk University, the most prestigious university in Korea. They are both accepted, but she does not reveal that she can not pay the tuition, and so she does not attend and lies to her family-in-law, telling them she will meet them in Seoul, not revealing that her mother is actually on the run. When Mong-Ryong finally does find Chun-Hyang, he tries again and again to reveal his feelings for her, while unearthing her feelings for him by moving into her new location. When he finally confesses outright, she denies him, claiming she never loved him, because of Chae-Rin's harsh statement that Mong-Ryong was merely pitying her and wished only to pay her back.
When the two finally do confess to each other, there is still one more problem. Byun Hak-Do, being rich, handsome and successful, assumes he could have any woman in the world, but when Chun-Hyang rejects him, he attempts to take her by blackmail. Several days before the real wedding between Mong-Ryong and Chun-Hyang, Mong-Ryong witnesses a woman being assaulted and attempts to save her. It turns out to be a plot, and so Mong-Ryong is now a criminal on the run. Byun Hak-Do carries an edited video of the security camera, putting Mong-Ryong in a bad light, and threatens Chun-Hyang that unless she goes to him, he will expose the video to the world. Chun-Hyang agrees and so Mong-Ryong is freed, but now, Chun-Hyang pretends to want to divorce him immediately to keep her end of the bargain. When the divorce is complete, she goes to Mr. Byun and the two of them prepare to travel to Japan, but at the last minute, she runs off and hides from both Mr. Byun and Mong-Ryong.
Several years pass and Mong-Ryong is now a famous prosecutor, the District Attorney of Seoul. Chun-Hyang has snuck off to Busan and now owns an accessories factory. Mr. Byun has just returned from Japan and people assume that his "fiancee" is still there as well. At the wedding of Mong-Ryong's and Chun-Hyang's two best friends, Bang Ji-hyuk and Han Dan-hee, Chun-Hyang sneaks in to drop off a present, and as she leaves, Mr. Byun sees her. In a rush to leave, she accidentally scrapes the car next to her, which is consequently Mong-Ryong's car. The two start a heated argument through Chun-Hyang's assistant, Kim Dong-Su, who goes to pay Mong-Ryong the money they owe for his car. Several crooks who follow assume Kim Dong-Su to be an informant and kidnap him. When the police rescue him, they discover the wedding picture from high school between Mong-Ryong and Chun-Hyang and show it to Mong-Ryong. When he sees it, he uses it to find Chun-Hyang again, but she still acts unhappy to see him, still frightened from knowing what Byun Hak-do has.
Finally, Byun Hak-do realizes that there are just some things in the world that he can't have, and finally releases the full unedited version of the tape so that everyone can see Mong-Ryong's true intentions and allows Chun Hyang to go back to Mong Ryong.
To add to the happily ever after, Mong-Ryong re-proposes to Chun-Hyang and the two are married again. And they live happily ever after.