Kase may be overprotective. But they all act like childs, without knowing what they might get into. Especially Yamada. Extremely shy towards boys and larger groups, so it would be easy to take advantage of her cause she's overwhelmed by the situation. So yeah, better have an overprotective helicopter watch over her. But i hope in the end, Yamada gets a bit more adult, and Kase supports Yamada a bit more in her decissions. 👍