
Here a whole reddit post for this: https://www.reddit.com/r/boyslove/comments/9swlj6/psychologicalhorror_bl_manga_recommendations/

-Itou-san: prostitute x hitman/yakuza murderer. Pretty twisted. (E)
- Escape; a short one with angst and abuse. A fav of mine as much as I remember. (O)
-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. (O)
-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.
-Sabita Yoru Demo Koi Wa Sasayaku; domestic violence. I really really love this author, and the characters felt very real to me. (O)
-Warehouse; careful I have never read it before, but I heard so much about it, especially about it being like KS.
-Moritat; also heard it was very messed up with a really good plot.
Now I will list things that I am gonna list next are things that aren't twisted, but are plot heavy and deal with heavy themes. They are also very dark, but the couple has a romantic relationship.
-Blood Bank: tbh I started that webtoon to fap (it has BDSM), but then gosh I wasn't expecting the plot, nor to fall for Shell. It has discrimination and action.
What about Dark Heaven? Set in a fictional city in Russia where gay marriage had become legal. Themes are homophobia, hate crimes, corruption, etc etc. It might not be what you are looking for since the main couple isn't exactly fucked up or twisted like Harada's or KS. They are the exact opposite. It has a very strong "love wins" theme.

-Itou-san: prostitute x hitman/yakuza murderer. Pretty twisted. (E)
- Escape; a short one with angst and abuse. A fav of mine as much as I remember. (O)
-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. (O)
-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.
-Sabita Yoru Demo Koi Wa Sasayaku; domestic violence. I really really love this author, and the characters felt very real to me. (O)
-Warehouse; careful I have never read it before, but I heard so much about it, especially about it being like KS.
-Moritat; also heard it was very messed up with a really good plot.
Now I will list things that I am gonna list next are things that aren't twisted, but are plot heavy and deal with heavy themes. They are also very dark, but the couple has a romantic relationship.
-Blood Bank: tbh I started that webtoon to fap (it has BDSM), but then gosh I wasn't expecting the plot, nor to fall for Shell. It has discrimination and action.
What about Dark Heaven? Set in a fictional city in Russia where gay marriage had become legal. Themes are homophobia, hate crimes, corruption, etc etc. It might not be what you are looking for since the main couple isn't exactly fucked up or twisted like Harada's or KS. They are the exact opposite. It has a very strong "love wins" theme.

https://www.mangago.zone/read-manga/black_mirror/
https://www.mangago.zone/read-manga/criminal_interview/
https://www.mangago.zone/read-manga/hikaru_ga_shinda_natsu/
https://www.mangago.zone/read-manga/kansai_jin_to_hukuman_satsujinki/
https://www.mangago.zone/read-manga/sleeping_dead/
https://www.mangago.zone/read-manga/madk/
Any horror yaoi guys?