Momoko married a man with a child from a previous marriage. She wants to get closer to her stepson, Yuta, but he keeps his distance from her. However, when she gives him advice about his declining grades at school recently... She learns that his sexual desire has not subsided and that he has become obsessed with masturbation. Momoko, as a mother even though she is a stepmother, risks her body to give her son a sex education. Yuta repeatedly climaxes as his stepmother teaches him how to control his ejaculation. Thanks to Momoko's efforts, the distance between the two gradually closes...