Japanese: 宇宙の死を見た不老不死

Alison (alison airlines)'s trilogy. What happened when immortals faced the End of Days?

First chapter: pixiv #50169854 (post #2010061)
Second chapter: pixiv #50169911 (post #2011395)
Final chapter: pixiv #56677797 (post #2351486)
"Eternity" chapter (draft): post #2584678