Topic on Forum:Trope Talk

Is the "many traditions" or the size of the family important? I'm trying to find a trope that fits what the fifth diary user from Mirai Nikki considered his 'ideal family', which consists of: Yuki's mom, Yuki, Yuno, and himself. He tries to kill Yuki and Yuno, and in turn Yuno tries to kill him, which he considers a game. And Yuki and Yuno's relationship so dysfunctional that I consider it a work of art.