Yuka raised her adult son Kosuke alone. As he grew to resemble her late husband, she developed forbidden feelings that she could only satisfy in private. Kosuke secretly loved his mother as more than family too. On the night before his wedding, Yuka catches him masturbating and gently strokes his thick, erect cock, calling it their last night together as mother and adult son. A handjob is not enough, and their suppressed desire drives them across the taboo line.