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.
Series
- Ghost in the Shell: Stand Alone Complex
- Black Lagoon
- Odd Taxi
- 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
+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 (unfortunately, the other related series Bubblegum Crisis and Bubblegum Crash are disqualified because Nene Romanov is 18 and Priss is 19, both under 20)
-
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)
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.
86
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.
Mushishi. Very serious, well-told stories told in single episodes. Occasionally a younger character will come along, but it’s mostly adults, and the cast outside of the MC rotates episode to episode.
I’ve completed quite a few:
- Violet Evergarden
- Vinland Saga
- Odd Taxi
- Cherry Magic!
- One Punch Man
- Saga of Tanya the Evil
- Delicious in Dungeon
Honorable mentions - depends on how strictly you’d define “mostly”:
Honorable mentions - unique circumstances:
- Cells at Work! - Your typical red blood cell lives for about 120 days :( The cells that look like adults do behave like adults though
- PLUTO - Robots’ mental age can be different from their physical appearances
The only one I’d take issue with here is Spy X Family. I think it’s more of an “all ages” show that focuses heavily on Anya and her classmates antics. All the rest make sense!
Saga of Tanya the Evil
Uhh, the main character is technically a child, even though they >!have the mind and soul of a middle-aged man!<. I’m not sure I’d include this, but the other characters still work.
The rest of the cast appear to be adults though.
One child among numerous adults satisfy the definition of “mostly adult cast of characters” that OP asked for IMO.
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) https://anilist.co/anime/19/Monster/
Mushishi (Psychological Slice of Life) https://anilist.co/anime/457/Mushishi/
One Punch Man (Comedy Action) https://anilist.co/anime/21087/One-Punch-Man/
TRIGUN (Action Adventure) https://anilist.co/anime/6/TRIGUN/
Hellsing (Vampire Action) https://anilist.co/anime/270/HELLSING/
Overlord (Evil Fantasy) https://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.
Overlord has Mare and Aura though? Who, ignoring numerical age, have the appearance of a person under 20.
And Victim is a literal fetus, though Victim is only in the show for about 3 frames.
Ghost in the shell stand alone complex (and 2nd gig) was my first and still favourite anime.
