no, the main female charc want all her brother attention to her own, and sabotage all his friendship with other girls. It seems to me that the main female charc is in love with her brother ,therefore the female:netorare tag
From what little Japanese I know the brother wants her to die and is scared of her proclaiming she's a demon when the teacher asks him what he thinks of her. The yandere agrees until the Teacher proclaims that the staff raping her will be her new older brothers.