Several months have passed since Satsuki Kirioka remarried and moved into the household. Since his mother left him 15 years ago, the son Ichitetsu has harbored deep hatred toward any woman who tries to take the role of "mother." Despite Satsuki's constant efforts to build a family bond, Ichitetsu refuses to speak to her at all. One day, a woman suddenly appears before Satsuki—delivering a letter meant for Ichitetsu. Upon receiving it, Satsuki learns this woman is actually Chisato Shoda, Ichitetsu's real mother. Unable to accept this truth, Ichitetsu begins to view both women as depraved, subjecting them to sexual domination. This twisted relationship unfolds dramatically, revealing the dark depths of Ichitetsu's psyche as the story of Two Mothers Being Kept spirals into incest, humiliation, and psychological torment.