My point is that we're discussing people who could attempt suicide and if you have to come up with a ridiculous scenario to make them crumble then it's not worth discussing as most people would also shut down at that point. Also it would not make for a good story.
For example Makoto's dad dying was a good event, because she was already at a bad mental state and the event push her down to the lowest point so that she could rise back up. And while Chinami dying out of nowhere would break Chika a lot, it would also not fit in with her story at all. Chika has her own arc and her own struggles and doesn't need her suicide story like Makoto. That's why I think most of the people on that list will not attempt suicide.
I think you're being a little too optimistic, tbh. Chinami has been teased to die since the cough, and her death or disappearance would easily make the Dark Phase, Dark. She is only a side character in the end. A very sickly one at that, that Sensei has grown close too. I can see her being fridged.
Tack on Chinami disappearing, then add something like Chika finding out Sensei is cheating, and I can see Chika getting suicidal. Not that I can see her being allowed to stay dead. It also wouldn't be the first time someone tried to kill themselves, broke, then got reset back to normal. Chika might even be reset to forget about Chinami, just to add some more darkness. Similar to the whole "Who's Ayane?" Sana thing, except for real. A Chika that suddenly doesn't have a sister to take care of, or a boyfriend to impress, would be interesting to see.
Chika's "struggles" and story revolve around stability. Not really sure why you think something like this couldn't be a possibility. It almost fits too well, imo. Then again, that could be the twist. It's so predictable, it won't happen.
I also think most people on my list won't commit suicide. It'd be far too excessive. I do think they all have the potential though.
