A high school student, Han Joon-soo (Jang Keun-suk),

is a troublemaker. He always quarrels with his parents and does not obey them. One day his parents are sick of his bad behavior and run away from home, leaving only a videotape and $100, stating they would come back when Joon-soo got his act together. Shrugging it off, he decides to just throw a small party with his friends, Ki-seok (Ko Gyoo-pil)and Choon-seung (Choi Jae-hwan), in his empty house. While buying alcohol at a grocery store, a baby with a note is left in his cart. The note claims the high school senior, Han Joon-soo, is the father of the baby and the mother could not take care of him anymore. The baby’s name is revealed to be Han Woo-ram (Moon Mason)

. Joon-soo finds himself stuck with the child, he tries abandoning Woo-ram multiple times, but always fails. Without anyone to help him, other than Kim Byul (Song Ha-yoon),

a smart girl who has a crush on him, Joon-soo resorts to bringing the baby to school and his part-time jobs. Finally, he is suspended from school due to the baby being a disturbance. After days of becoming financially broke and sinking to the bottom, his parents come back home when Joon-soo has an emotional breakdown and expresses his sympathy and love for the baby; a love that changed him from troublemaker to a caring father. Joon-soo's parents acknowledge their love for their son and tell Joon-soo that they will help take care of Woo-ram. When Woo-ram is admitted to the hospital, Joon-soo becomes depressed and meets up Ki-seok. Ki-seok tells Joon-soo that he himself is the father of Woo-ram. Furious, Joon-soo beats up Ki-seok and tells him to take Woo-ram back. He later lies to Byul and Choon-seung that he does not care about Woo-ram anymore. Woo-ram, now out of the hospital, is being adopted by a couple from overseas. After contemplating, Joon-soo races to the airport and fights his way through security. At the gate, he yells for the couple to give Woo-ram back to him. Later, Joon-soon agrees with Ki-Seok that they will raise Woo-ram together. Byul sends Ki-seok and Choon-seung to go buy some soda, wanting to be alone with Joon-soo. After she coyly compliments his "cool" behavior at the airport, Byul gives Joon-soo a quick kiss before running off.

Cast

Jang Keun-suk as Han Joon-soo

Moon Mason as Baby Woo-ram

Park Myeong-su as Baby Woo-ram (voice)

Song Ha-yoon as Kim Byul

Ko Gyu-pil as Ki-seok

Choi Jae-hwan as Choon-seong

Kim Byung-ok as Joon-soo's father

Park Hyun-sook as Joon-soo's mother

Jung Gyu-soo as Kim Byul's father

Jang Jung-hee as Kim Byul's mother

Song Min-hyung as Vice principal