"Big Sister! What are you doing?" While his wife was visiting her family for a home birth, Toshiya was enjoying a brief taste of bachelor life. However, he was suddenly interrupted during masturbation by his sister-in-law, Erika, who called out to him from behind. It seems she came to check on him, worried about his being alone. By the time he hurriedly tried to hide his crotch, it was too late. Seeing Toshiya's erect penis, which had been pent up due to his wife's absence, Erika approached with a knowing smile, as if plotting something. There was only one week left until his wife's due date. A dangerous cohabitation with his erotic and free-spirited sister-in-law had begun.
