In the Kotatsu, he secretly played a sluggish role: his sister-in-law was so cute that he couldn't control his desires.

One day they suddenly became sister-in-law. Even though he is an older brother and sister, his blood is not connected to other people in red. I haven't become a "family" yet, but we are at home alone. My brother-in-law, who was jealous of her cute little sister who lived in defenselessness with kotatsu and became unbearable, was a wretched prank in the kotatsu. My sister also became interested in it and committed a serious crime. Three of his sisters, S○X, were included with his brother-in-law.