I'm looking for books with murderers or psychotic characters, who kill people, keep people prisoner, or make others kill people.
Whether they're the MC or the one doing it to the Mc I don't care.

I'm mainly looking for male/male relationships or friendships. But I don't mind other suggestions.

Also it doesn't have to be manga, it can also be Manwha, Manhua, or even novels.

Thank you.

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Fujoshis rule!

Anorexia - Shikabane Hanako wa Kyoshokushou, Boku Dake ga Inai Machi, Hanged Doll, Hwaja, Killer Stall, Kiseijuu, Melo Holic, Murasakiiro no Qualia, Sakura no Sono (FUMI Fumiko), Superior Day and Yuureitou

Koroshiya Ichi is a pretty perfect fit for your request.
Tajuujinkaku Tantei Psycho
Blue Heaven
Deathco
Dolls Fall
Kami no Kodomo
Mahou Shoujo Site
Monster
Museum - "The Serial Killer Is Laughing in the Rain"
Destro 246
Wolf & Mary -- Though this is a bit wacky.
Hellsing
MW
Rinjin 13-gou
Satanister
Doreiku - Boku to 23-nin no Dorei
Ookami no Kuchi: Wolfsmund
Korokoro Soushi
Becchin to Mandara, Freesia, and almost anything by Matsumoto Jiro.
Overlord (Novel)
Funouhan

There are lots of other good suggestions for this, but with prominent male/female romance. I'll mention them anyway, because they all have psychotic MC's or feature torturers/killers as important characters:

Ayeshah's Secret
Ana Satsujin
Doctor Du Ming -- You might wonder why I rec'ced this at first, but keep reading.
Bastard (HWANG Youngchan)
Berserk
Crying Freeman
Anne Freaks
Kamisama, Kisama o Koroshitai
Nijigahara Holograph
Redrum 327
Tsumi to Batsu - A Falsified Romance
Jigoku no Alice
Deadman Wonderland
Shigurui
Elfen Lied

Last edited by calstine at 8:48 pm, Feb 20 2017

Killing Stalking kinda has this premise. I think..

Killer Killer (MC kills people)
Jinrou Game (MC holds a girl prisoner)
Bastard (HWANG Youngchan) (Psychotic characters)

Quite a few suggestions in this thread and yet The World Is Mine went overlooked.

It hits pretty much every aspect mentioned in the OP. Killing people, keeping people prisoner, making others kill people, male/male relationship/friendship - it's all there.

Hmm pshychotic characters or characters that do evil deeds is pretty broad. I'll list some that haven't been listed yet I guess?

Doubt (TONOGAI Yoshiki)- People wake up in a place and have to try and escape their prison while the murderer slowly kills them off one by one. Its more mystery and psychological suspense.
Hideout-Very interesting where the MC ends up in a horrible situation and tries to escape before his mind has been swallowed by the darkness.
Akumetsu- Very graphic and gory where the MC kills people in the name of justice. Not really psychological, but it does parody real people from the Japanese government (I was actually able to recognize one without the translator's notes xD).

Doubt -Haven't read this but its male/male + mystery + death, so your cup of tea ?
Caste Heaven -A lot of male/male abuse with pretty characters that have black souls :x.