Responses

i think he always had issues. in the extra scene where they went to the beach, he mentions how the memory won't last and how mafuyu is gonna forget about him, foreshadowing his death. his mother mentions how his "will to live is drifting", and she thought that mafuyu was like his anchor that kept him sane. it's also mentioned how he was always trying something new, and "crossed a line" that night. he reacted to a small argument dramatically which led to getting drunk and hanging himself, because he felt like his anchor was gone.
I still need more back story on his death. Was he intoxicated with the alcohol and that made him jump. Did he think he will be fine after doing that. I think he is a fearless guy that does risky stuff without thinking twice.