Toge Inumaki is important too. His special cursed speech ability makes him stand out. Also, the principal of the school, Masamichi Yaga, is likely to be important as he is in a position of authority and has an influence on Gojo and the other students. There could be other characters like the members of different clans that also play roles in the complex web of the story.
It could mean that someone is asking another person if they really want them to kill a particular 'him'. It might be part of a very disturbing or serious situation in a story. Maybe there's some deep conflict or vendetta involved.