@Tamerlane
I think you might want to give this a look, cause no one actually wants to live forever for many reasons:
https://mangadex.org/title/22440/jumyou-wo-kaitotte-moratta-ichinen-ni-tsuki-ichimanen-de
I have to mark this because I'm not good at information separating or else.
I really love the manga, and it really makes me chill out for a while of stress from works. I did not mean to be a psychologist, just my thoughts after reading over a bunch of psychological mangas.