[TOMT] "I can't save you because you are already dead" - likely movie/tv series

I don't remember the clear details, the plot was something about a deep relationship developing between two people, where the main character has to save that other character, but right before the end there is the realization (either from the protagonist or from the other character) that that character is dead, hence it cannot be saved. The media ends on a bittersweet note, with the feeling of "I failed to save them". I remember the timeline being fuzzy, could have been alternate realities, sort of dreamlike, sort of unreal, but based in the present and not too over the top. I am kind of reminded of "the eternal sunshine of a spotless mind", but it's not that. It also has some of the vibes from "the view from halfway down" of bojack horseman.

I very recently saw another piece of media with a trope like this and I was like "wait- this reminds me of something" but I cannot pinpoint what at all. I am desperate, please help!