Boku no Pico
Season 1, Episode 2: Pico & Chico
Select Source
Pico finds a boy named Chico swimming nude in a stream, and the two become friends. Later at Chico's house, Chico takes Pico to his attic, where the two spy on Chico's sister masturbating. Pico then shows Chico that boys can also do this, and the two have sex.
