I think some people are saying this too, but I think Asaka (the black haired girl) will die. Probably at the end of the summer, as it is referred to multiple times that this was the last summer white haired girl will spend with her. Also you see Asaka getting sad quite often, and white haired girl says that something feels off. Im not quite sure why Asaka (and my apologizes if thats spelt wrong, Im not very good at spelling) wants to date White Hair.
I saw a comment theorizing that MC will die by suicide. I dont think thats going to happen, because the plot is appearing to be something more of: Black Haired Girl wants to give MC hope/a reason to live, and then probably dies herself.
But thats just my theory. Cant wait for the ending.