Manga by author Kotsume Rokku - Status ongoing

The two of them know each other's fap material, and they even rub each other out. Such childhood friends are Junto and Sato. One day, the AV that a classmate lent them showed a**l sex! Sato, gushing with curiosity, says that he wants to try it, and begs Junto to put it in. Junto gives in to the seduction, and...!