Nikaidou doesn't know yet that Kirigaya is an evil bully who made Tadokoro's life miserable during middle school... right?
Oh dear. Wait till she finds out.
I foresee a scene in the future where Tadokoro-san (who is an angel character) will need to say: "No, Nikaidou-san, stop, don't pummel Kirigaya-san into hamburger, I have already forgiven her, really I have."