After his wife went back to her parents' place for childbirth, Koji was left alone. His wife's sister, Mizuki, offered to take care of him. Struggling with both work and house chores, Koji gladly accepted. However, when Mizuki insisted on helping with bathing, they ended up in the bath together. Koji couldn't help but react to Mizuki's beautiful naked body. Noticing this, Mizuki said, 'You got hard because of me? That makes me happy...' and forcefully approached him…
