The protagonist is asked by his mother, Kaori, to be a temporary coach for her Mama Volleyball team. The team is weak and has been losing, so they turned to the protagonist, a former volleyball team member. He expected the team to be full of middle-aged women, but instead, the team is full of curvy, mature women, including Kaori and her friends, Chie, Nozomi, Yuuri and Kyoko. The protagonist is overwhelmed by their voluptuous bodies, and the women take advantage of his naivety and engage in sexual harassment. Meanwhile, Kaori worries about her son's virginity.