One week ago, Sohta's wife returned to her parents' home as she approached her due date. While praying for her safe delivery, Sohta found himself lonely, spending each day alone. To cheer him up, his wife's older sister, Ranka, came to visit. Noticing that he hadn't been intimate with his wife throughout her pregnancy, she bluntly asked, "You must be all pent up, right?" Flustered yet unable to resist Ranka's stunning figure, striking beauty, and voluptuous body, Sohta eventually gave in and ended up having sex with her.