Recommendations for Bad Children, Vol. 2 (novel) — Setsuka Narumi

Ren and Kurumi successfully crash the school festival, but their rotten reality won't change so easily. In only a few days, their hellish prep school is back to business as usual. But as they're cooking up a new plot to disrupt summer classes, the school's top honors student approaches them with a shocking revelation—she knows what they're up to, and she wants in. She's planning something big to prove herself, and Ren and Kurumi will have to pull off something even bigger to stop her.