My parents remarried, and my mother's stepfather Rika became my sister-in-law. I live alone, and my sister-in-law also lives in the staff dormitory and I don't live together, but I'm worried about my sister-in-law. One day, when I return from night shift, there is a sister-in-law in front of the entrance... If you invite me to the house, I'll be in a dangerous relationship with you.