デスゲーム漫画の黒幕殺人鬼の妹に転生して失敗した (Associated Names)

One day, Mai remembers that her perfect stepbrother is a character in a death game manga and that one year later he will hold a death game involving all of his classmates, killing his sister in the process. Mai plans a variety of surprises for her stepbrother every day based on what he said in…