The film tells the love story of a male engineering college student, Gyeon-woo (Cha Tae-Hyun), and the Girl (Jun Ji-hyun) who is never named in the movie. Gyeon-woo just cannot seem to catch a romantic break. One day, at dinner, Gyeon-woo is interrupted by a call from his mother, telling him to visit his aunt and meet a potential date. At the train station on his way to his aunt's, he observes a drunk girl, standing precariously close to the edge of the train platform as the train approaches; he pulls her to safety just in time. Inside the train, Gyeon-woo cannot help but stare at the girl who is his "type" but repulsed by her drunkenness. Finally, she throws up on a passenger and faints but not before she calls Gyeon-woo "honey". The passenger aggressively chides Gyeon-woo and tells him to take care of his "girlfriend". Gyeon-woo, completely flustered, carries her all the way to the nearest hotel. Thus begins his comically ill-fated relationship with the Girl whom he realizes is a xanthippe. They meet each other again after Gyeon-woo gets locked up in jail over a misunderstanding, and over soju the Girl cries, admits to breaking up with her boyfriend the day before and gets thoroughly drunk, resulting in a second trip to the same hotel.
After this second overnight stay at the hotel, she begins to become a more active part of his life. She visits Gyeon-woo in school and pulls him out of class, telling the teacher that Gyeon-woo is the father of her soon-to-be-aborted baby. The Girl's mood swings wildly from joyful to downright violent, but Gyeon-woo puts up with it and lets her abuse him for her amusement.
She is an aspiring scriptwriter and throughout the movie gives Gyeon-woo three different screenplays from different genres. The first is an action movie—The Demolition Terminator—which switches gender roles, symbolically having the Girl save her helpless lover (Gyeon-woo). The second is a wild perversion of a Korean short story—Sonagi—in which the Girl, having died, asks that her lover be buried along with her—even though he's still alive. The last is a wuxia/samurai movie spoof full of genre clichés and anachronisms. All three feature the same common thread: the Girl is from the future.
Despite all the horrible things Gyeon-woo endures, he is determined to help cure the girl's pain. He decides to surprise her on her birthday and takes her on a nighttime trip to an amusement park which ends up quite differently than how he planned: the pair encounter an AWOL soldier who holds them hostage and rants about his misery after being jilted. Gyeon-woo convinces him to release her, and she in turn convinces the soldier to free Gyeon-woo and go on with his life and pursue another love.
