By adult I mean over 18-20 years of age and with adult appearances. Nothing against anime with younger characters, but interested in finding some with older characters.
In no particular order these come to mind. Most of these are outside what I typically watch, but I did enjoy them.
Monster (Crime Drama) anilist.co/anime/19/Monster/
Mushishi (Psychological Slice of Life) anilist.co/anime/457/Mushishi/
One Punch Man (Comedy Action) anilist.co/anime/21087/One-Punch-Man/
TRIGUN (Action Adventure) anilist.co/anime/6/TRIGUN/
Hellsing (Vampire Action) anilist.co/anime/270/HELLSING/
Overlord (Evil Fantasy) anilist.co/anime/20832/Overlord/
I think a lot of the other answers here are being too generous with your rules and not giving you characters that both look older and are older.
earth_walker@lemmy.world 2 months ago
Series
Ghost in the Shell: Stand Alone Complex Black Lagoon Odd Taxi 86 Moriarty the Patriot Cells at Work: Code Black Cowboy Bebop Trigun (1998) Psycho Pass Aggretsuko Panty & Stocking One Punch Man
Movies
Patlabor Patlabor 2 Ghost in the Shell (1995) Ghost in the Shell 2: Innocence Redline Porco Rosso Howl’s Moving Castle Paprika Dead Leaves
RightHandOfIkaros@lemmy.world 2 months ago
+1 for Black Lagoon, W anime pick.
Also for Ghost in the Shell, PatLabor, and Redline.
I will also add on:
Jin-Roh/Jin-Rou (not the Korean live action from 2019), but it does briefly show a child on screen as a supporting character, and I dont remember if Kei was over 18-20 or not
AD Police Files, and its related series Parasite Dolls
Space Dandy (maybe, that anime had like a billion characters and I dont remember if all of them were adults or not, but its not exactly a kid oriented anime)
earth_walker@lemmy.world 2 months ago
Black Lagoon is one of the most underrated shows. People who have seen it usually love it, but not enough people have seen it.
I need to watch Jin-Roh sometime.
nevemsenki@lemmy.world 2 months ago
Patlabor 2 is one of my all-time favorites, but it’s not very well-known. In a way it feels too mature and slow to be a wide hit, I guess.
Endmaker@ani.social 2 months ago
The main cast would have grown into adults later on, and based how what’s released of the anime so far, I wouldn’t count it as “mostly” adults.
earth_walker@lemmy.world 2 months ago
You’re right, I misremembered how old the characters were. I removed it from my post. I must have thought that because it dealt with a lot of mature themes and war kind of forces kids to grow up fast.