MANGA Similar to Kurozakuro . World Embryo , Rosario to Vampire , Aflame Inferno , Alive: Saishuu Shinkateki Shounen , Togari and Togari Shiro

The only difference between saints and sinners is that every saint has a past while every sinner has a future. - Oscar Wilde

The stories you are quite dark & ecchi (with exception of Rosario to Vampire being more comedic than dark). Hmmm..... how about Shinrei Tantei Yakumo(no ecchi stuff but quite dark), Psychometrer Eiji, Ubel Blatt, Taboo-Tattoo, Psyren and some other stuff I can't quite remember at the moment. If none is helpful, then I won't bother to list the rest cause you won't like them anyway.

Have you read Hoshi no Samidare?
How about Mirai Nikki?

You could try Tegami Bachi or D.Gray-Man

If you're looking for dark with comedy, I'd say Pandora Hearts and Kuroshitsuji. Maybe also Darker than Black and Are You Alice?

I am vindicated!
I am selfish;
I am wrong!
I am right,
I swear I'm right.
Swear I knew it all along
And I am flawed!
But I am cleaning up so well
I am seeing in me now
The things you swore
You saw yourself...

~"Vindicated" by Dashboard Confessional

you could try :
immortal regis
Zero
Shade:the otherside of the light
shaman king
the law of ueki

Words to live by: "Let sleeping dogs lie"
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Shingetsutan tsukihime
Yumekui merry

Being alone is only lonely if you want it to be.
Staying in lucid delusion for an eternity.