Growing up as the best of friends, Sang-doo (Bi) and Chae Eun-hwan (Gong Hyo Jin) make lots of lasting memories during their shortened high school years. When Eun-hwan's family goes into bankruptcy, debtors rush into their house to grab all of her family's belongings away. When somebody takes her father's old record player that she really loves, Sang-doo goes after the guy. In a physical fight, the man falls off the bridge and enters a coma. Eun-hwan, not knowing this, runs away from the town. Sang-doo goes to jail, returning to find out that his family and Eun-hwan have left him. Years later, he becomes a gigolo (with his uncle) in order to raise the hospital bills for his sick daughter (Se-ra (Hong Soo Hyun) claims that Bori is his daughter). Eventually, he meets his long-lost first-love, Eun-hwan as a high school math teacher.
