3P, Hajimemashita!

Gorou accidentally witnesses his childhood friends and twins, Itsuki and Satsuki, making out with each other and what's more, he gets excited by it and masturbates. The twins discover his secret peeking and confront him, only to be met with vehement denial. "I'm not interested in guys!" Gorou insists. But the twins have a few tricks up their sleeves to make him admit otherwise.