It's not a game
specifically about death, but death is a big element in the story thematically (if not the dominant one). I also guarantee it's unlike
any other game you have likely played, and probably a more unique experience than any single other game being mentioned ITT.
The English translation came out ~ 2 years ago but until then it was a Japanese exclusive. It's also one of, if not the, last Quintet game ever made. Seriously, give
Planet Laika a play; I'll be replaying it again over the holidays.
A good runner-up I could throw in there is
Cosmology of Kyoto. I need to replay this one again sometime, but it was a very enjoyable play the first time around. Also packed with a lot of interesting info on myths and historical events of Kyoto during feudal periods.