Nobuo has long harbored feelings for his stepsister, Rimu. After leaving his marriage due to discord with his spouse, Rimu returns to live with her family, reigniting Nobuo's nostalgic longing and fueling his fantasies. One night, Nobuo witnesses Rimu and his stepfather engaged in an intimate act. Overwhelmed by shock and arousal, he confesses everything to Rimu, and the two passionately embrace. Their emotions spiral out of control, driving their relationship into deeper, forbidden territory.