@Jeikob I've been thinking that too since the ending of chapter 3.5 but I feel a little better after seeing the Mom in the colored spread in this chapter
They better not make the little sister a romantic interest it just makes the story all messy. I'm pretty sure everyone wants class pres to win anyways.
@otb I was referring to the novel, if I remember correctly decapitating them was Sansui's decision. He wasn't asked to do it.
@primrosea tell that to the author I was just going by what's in the novel
Sansui has no problem with killing but it's wasn't supposed to be an order to decapitate everyone just to kill them. Decapitation is simply Sansui's preferred method because it's efficient and almost painless for the other person since it's instant.