Bullied high school student Soo-hyun jumps from a school rooftop but unexpectedly lands back on the roof. There he meets three boys—Da-in, Seung-woo, and Ji-hoon—who died 15 years earlier. Because Soo-hyun can see them, they ask to borrow his body to fulfil their unfinished wishes before crossing into the afterlife. In return, they promise to help him.

Possessed by the academically gifted Da-in, Soo-hyun excels in mathematics. With Seung-woo’s basketball skills, he also impresses Jong-woo, the discouraged coach of the Sang-rok Little Basketball Team. The struggling team has only four players and faces disbandment unless it wins a game. Soo-hyun becomes its fifth member, allowing it to enter a tournament.

During a trip to Sokcho, Da-in sees his father, who returns to the beach every summer with the snacks his dead son loved. Unable to reveal himself, Da-in asks Soo-hyun to accept the food in his place. The team later defeats a local elementary-school team, and Soo-hyun is appointed captain, causing tension with Sang-tae, its most dedicated player.

When Soo-hyun is bullied again, neither the ghosts nor Sang-tae help him. Feeling abandoned, he returns alone to the court, where Jong-woo challenges him to a game. A familiar expression used by Seung-woo makes Soo-hyun realize that the three ghosts were Jong-woo’s childhood friends.

Fifteen years earlier, the boys died while rescuing drowning children in Sokcho. Jong-woo, unable to swim, remained onshore and has carried guilt ever since. Reunited with the ghosts, he plays one final game with them. They tell him they have always watched over him and ask him to become a good teacher before disappearing.

Sang-tae gives Soo-hyun a new whistle and accepts him as captain. Although the team loses its next tournament game, an earlier victory by default satisfies the requirement for one win, saving the team from disbandment.