Okaa-san no Ama Ama Time ~Poolside de Nanpa Lesson~

At a swimming pool with his mother, she discovers that he has never even tried to pick up girls. Worried about the shy protagonist, Mom asks him to be her training partner. He gives her a massage as a form of skinship.

Normally, she is an unobtrusive, intelligent, and calm woman, but as he compliments her on her swimsuit and caresses her body, her breathing becomes raspy.

Seeing her like that, the protagonist really wants to pick her up....

[From official site]