
Please give me some recs too!! HxH 1999 has some dark aspects, Perfect Blue is pretty intense. Swan Lake 1981 isn’t really dark, but I really enjoy it as well and there’s an English dub on YouTube that I think is pretty good. Graveyard of the fireflies is good and depressing. Paprika is trippy and a great critique of Japan. Cowboy bebop is a good seinen but not very serious.
I think it’s easier to find mature mangas than mature animes partially because mangas are less restricted and also because mangas typically take a mangaka a lot of years to finish so a lot of good ones start in the 90s and end in the 2000/2010s. Tokyo Ghoul is an amazing example of this