Kuromaku Ikka ni Tensei Shita kedo Gensaku Mushishite Dokuritsu Suru

The protagonist, who has been reincarnated into the world of a game he played extensively, has become Yuri, the third son of a villainous family!! His father, siblings, and the entire household are the worst and most ruthless, all doomed to be brutally massacred. As for Yuri himself, he is destined to betray the Hero as the final boss, dragging the heroine down with him to meet the worst possible fate.