yass

-Itou-san: prostitute x hitman/yakuza murderer. Pretty twisted.

http://www.mangago.me/home/mangalist/98787/?filter=manga

- Escape; a short one with angst and abuse. A fav of mine as much as I remember.

http://www.mangago.me/read-manga/escape_kyuugou/

-Sora o Daite Oyasumi; first manga that got me into twisted stuff. I remember when I first read it, my heart was endlessly breaking. Warning, it had been axed, but honestly I can't imagine another ending to the manga either.

http://www.mangago.me/read-manga/sora_o_daite_oyasumi/

-Sakura Gari: apparently it is very plot heavy, tragic, etc. The thing is, when I tried reading it two years ago, I couldn't get into it. Lots of people praise it, though.

http://www.mangago.me/home/mangalist/291142/

-Sabita Yoru Demo Koi Wa Sasayaku; domestic violence. I really really love this author, and the characters felt very real to me.

http://www.mangago.me/read-manga/sabita_yoru_demo_koi_wa_sasayaku/

-Warehouse; careful I have never read it before, but I heard so much about it, especially about it being like KS.

http://www.mangago.me/read-manga/warehouse/

(from reddit)

if its more to psychological and not abt the fluffly love u want at the end then

-easy target
-colour recipe ( didnt know he was a tsundere till near the end, he tricked even me as a reader )
-Kiyoku Tadashiku Utsuku Shiku
- the perfect relationship

personally i think all of them are gd psychological mangas but easy target n the perfect relationship is messed up

I cried bc of this one, I'm not even kidding. It's one of my favorite and it's so damn realistic =
http://www.mangago.me/read-manga/smells_like_green_spirit/
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those are kinda dark, they're all about yakuza =
http://www.mangago.me/read-manga/acid_town/
http://www.mangago.me/read-manga/canis/
http://www.mangago.me/read-manga/saezuru_tori_wa_habatakanai/
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This one is twisted as fuck but you asked for something psychological so.... :') =
http://www.mangago.me/read-manga/tourou_no_ori/
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And this one is really sweet and interesting =
http://www.mangago.me/read-manga/hotel_phryne/

This will stay one of my favourites,

http://www.mangago.me/read-manga/ore_higaisha/