I have several, but if I must pick one, it’s A Place Further Than The Universe. Interestingly, it’s simultaneously the happiest, too.
It wasn’t the case at first, but when I rewatched it, I was purely, emotionally devastated.
My kneejerk reaction to the question is “Grave of the Fireflies”.
It really is in a class all its own. I don’t think I could ever watch it again.
I haven’t been able too either, ~17 years later. I honestly feel like it gave me PTSD.
Your Lie in April and Angel Beats! both crushed me 😭
spoiler
It pretty much takes place in a limbo/purgatory. Children who die without finding peace or have unresolved emotions end up there. The story slowly reveals this and explores each characters’ reasons for ending up there - often confronting their death and untangling the things which kept them from moving on. Time itself is kind of nebulous there; two of the main characters, one who starts as a sort of antagonist and the protagonist, are kind of tied together by fate with the protag being a heart donor to the antagonist. The protagonist died before and his heart was given to her, but somehow she ended up there before him even though she lived a full life (if I’m remembering right) l. It’s honestly a super beautiful story, and I think one of my favorite parts is the ending song/mv which plays at the end up each episode- it features every character, and as they move on during the series their spot in the ED is just blank with the final episode ending without any of them.
Tap for spoiler
I absolutely agree 😭 But didn’t the post credits scene after the last episode suggest at least some hope for all of them? (Or am I seriously misremembering this because my brain tried really hard not to think it was over?)
Oh mate, clannad was sad
Your Lie in April. Easiest choice I’ve ever had to make.
I don’t usually watch sad stuff so Welcome to the NHK is probably the saddest I’ve seen.
