The boy went to his lover's house to play, and while he happened to be looking for the toilet, he discovered that his lover's biological sister, Yua Mikami, was having sex with her boyfriend in the bedroom, but she had a hobby of SM (meaning sadism, referring to people who have a habit of torturing and hurting their partners). While she was forever obsessed with peeping, she was caught by her, knowing that she was being peeped, so she took the initiative to find and seduce her sister's boyfriend, bringing him into her extremely perverted sex affairs, but it didn't matter, because she was so beautiful, and beautiful, it's all right =)))