I bet it's that student council president who called in 11. She's unhappy with Setsu's harem, and now she's forcing a cliffhanger on us to make all of us suffer as well. As expected of the sadist
Ch. 43 spoilers: We haven't actually seen Setsu die before now (or at least I assume she's dead), so I'm not even sure she could recover by going to Zin even if it hadn't closed. This is gonna be interesting.