Yuka lives with her husband Tadashi's father, Tetsu, who retired and moved in with them. Yuka does housework while working part-time, and Tetsu is an early riser, starting his activities at 6 AM every morning. Tadashi wakes up at 7 AM. During this one-hour interval, Tetsu secretly enjoys watching Yuka. However, driven by his growing desires, Tetsu one day rapes Yuka, ejaculating thick semen deep into her vagina. From that day on, during the brief time before Tadashi wakes up, Yuka is repeatedly subjected to Tetsu's internal ejaculations and gradually begins to awaken to pleasure…
