Haruna is a lively tomboy in the 5th year at elementary school. One day, while playing with Hiroyuki, a boy whom she has known for a long time, they play a game of putting their private parts together. A sex education lesson given by a new teacher, Yagi, makes Haruna suspect that she might be pregnant.

Masashi, a 15 years old school boy and so-called 'overprotected child', lives with his parents in the suburbs of Tokyo. Poised to graduate from middle school as per his parents' hope and expectations, Masashi experiences an incident during spring break that changes his life forever.