The protagonist, Minegishi Watari, lives together with his mother, Satomi. His father died when he was young, and his mother raised him all by herself. One day, to express his gratitude, he gave his mother a massage. However, Satomi's voice caused him to get an erection. He tried to hide it, but his mother still noticed it and gave him a blowjob, which made him ejaculate all over her face. Despite this event, they returned to their usual mother-son relationship. Until one day, when he saw Satomi masturbating......