Based on the erotic game by Beelzebub.

His name is Kareki Tsunetaka. He has been a so-called security officer at his home for 20 straight years. In reality he’s just a shut-in. I re-married to his father, bringing along with me two daughters, Sayaka and her younger sister Yuki to live with him and his father. However, Tsunekata does not find this agreeable. He causes trouble for us as he tries to make us leave. His target is Yuki. She seems to be doing something in her room lately. She apparently is worried about her bust size, but she’s already plenty cute. Oh no, Tsunetaka is staring at her with a scary face. I feel like this has happened before… Am I just imagining things? If only I made that decision at that place and time…