The main character is a virgin stay-at-home 'otaku'. His job is home security. By chance, his father remarried and made a new family. ..Sister-in-law. Of course, her eyes were cold when she looked at me...and violent.

However, I both gasped and struggled with my sister-in-law in my new family. My sister-in-law's sharp tongue was like a pressure point for me. Then one day, I could not stand it any longer, and I determined to go out night crawling on day X in month X in year 20XX. If I got caught I would be looked at even more coldly and may get punched and kicked. I had to have sex with her without waking her up.