Masaki has grown up as a mama's boy, receiving abundant love from his mother Iroha. His sexual desires have always been focused solely on Iroha, and the two are already engaged in a sexual relationship. Their secret encounters happen regularly, and though Iroha knows her body craves Masaki, she struggles with the moral dilemma of their forbidden bond. One day, her husband suddenly announces a last-minute trip for the two of them, leaving Iroha with a fleeting sense of unease.