Based on the erotic game by Marine.

Shin belongs to a cheer group. Though he wasn't interested in it, Yuko, his older step-sister, forced him to join it.... As a matter of fact, there are only two members, Shin and Yuko. On the other hand, a cheerleading club has a lot of members. One day, Shin accidentally collides with Chieru, a member of the cheerleading club, and she gets injured.... In compensation for her injury, he decides to work as a caretaker of the cheerleading club. But days later, Satsuki, a coach of the cheerleading club, suddenly orders the members, "You should give him a titjob to overcome your sense of shame!" As they are all confused, Satsuki starts giving Shin a titjob...!

(Source: Erogeshop)