Two high school boys, Tooru and Nao, have been best friends since kindergarten.

When they were in junior high school and were both curious about sex, the two formed a no-girlfriends alliance, which prohibited them from sneaking around, and before they knew it, they had become friends who would vent their sexual desires with each other.

Now that it's become commonplace for them to masturbate, Tooru is troubled by a certain secret that he can't even tell Nao.