Psycho pass.

Paranoia Agent. Most of the characters there are adults if that’s what you mean?

How about . . .

• Berserk
• Black Lagoon
• Dorohedoro
• Psycho-Pass
• The Skull Man
• Zipang (I’ll place a warning on this one for a treatment of WWII on the Pacific Front that many people are not comfortable with. It’s an interesting, nuanced show if you can stomach it.)
• 91 Days
• Heat Guy J

I admit that I’m not sure of the licensing status of some of those.

Full Metal Alchemist Brotherhood.

So I guess you want to get more mature recommendations?

To your eternity - very beautiful, but not finished yet

Ghost in the Shell - a must watch

Samurai Champloo - very fun

Texhnolyze - just watch 1 or 2 eps to see if it is for you

Serial experiments Lain - not about adults but confusing and more Seinen I’d say

Hellsing Ultimate - gory vampire hunter series that also is a bit silly

And of course the Ghibli movies are highly recommended

There are already some good recommendation in this thread and I will second some of them in my list:

• Baccano!
• Kino’s Journey: Yes, the main character is not an adult, but it handles very mature themes and is similar in feel to Mushishi
• Ghost in the Shell
• Samurai Champloo

Perfect Blue

Hellsing or Hellsing Ultimate

Spy x Family

Welcome to the NHK

Hunter x Hunter (2011)

Attack on Titan

Princess Mononoke

• Legend of Galactic Heroes
• Uncle from Another World
• The Garden of Sinners

Golden Kamuy

Violent criminals, samurai, vintage weaponry, cool uniforms, treasure hunts, animal fights, great characters and story. It’s got it all!

Steins Gate

Crazy sci fi adventure in a present day setting, surprise characters and plot twists, loveable characters, and you never know what will happen next.

Odd Taxi