Mariko, who has been a little disgusted with her peculiar propensity while spending calm days with her husband. Her player's brother-in-law, Kenta, sees through her secret frustration. Mariko is persuaded by Kenta, who skillfully pokes Sukehira's heart that sleeps deep in her, and entrusts herself to his fingertips as if she is being swept away. Her delicate and bold caressing easily melts her vaginal walls, gradually unraveling her rigid mind and body. At some point, Mariko tells herself, "I'm just being naive...".