I just realised reading this again, the way the story is going, with Reiji possibly going to Tokyo after Nagi and Sensei going after Chako, there is a non-zero chance that Chako commits suicide before Reiji gets back.
Reiji goes to Tokyo, Chako can't communicates with him, she goes to Esemori, he tells her that Reiji went after Nagi and she feels abandoned and has nothing left and offs herself