Ana Satsujin
DEAD Tube
If you don't mind high levels of brutality, excessive nudity, and other psychological shit, I recommend trying out this manga. It is, by far, the BEST HORROR/SLASHER manga out there (for me). The mangaka is very familiar and experienced in drawing the "ecchi" scenes, and does so while displaying a brutally shocking amount of gore for horror fanatics. Gotta keep an open mind before reading this one tho :P
Dolls Code
An awesome, quick read if you're itching for mystery and suspense ;)
Friday: Forbidden Tales
Okay. You're not gonna love the art but you definitely WON'T regret reading this one. This webcomic is messed up in many levels, it has very obscure storylines and deep sht that some of us actually think about. Think: end of the world, creepy stalkers, reincarnation, psychos, UFOs, war—and reality. What's scarier than that?
Ou-sama Game - Kigen
Read it in one go. I couldn't sleep anyway for two reasons: first, it's just TOO AMAZING, the way of killings are on point, the art style is beautiful, there's enough mystery to keep you reading, the plot twists are unpredictable... second, it ENDED. Btw this is the prequel of the first manga, "Ousama Game". Read that one first bc this is about the origin of the "Ousama".
Ousama Game ( Kanazawa Nobuaki )
Unsatisfying ending but an enjoying read. There's enough gore to keep you reading, and halfway to the end things got reaaally intense. Like people doing immoral things to save their own skins, and a mystery figure giving out insane commands with their lives on the line. Read the prequel "Ousama Game - Kigen" after this one.
Ou-sama Game - Shuukyoku
Sequel of Ousama Game.
Tokyo Red Hood
A very disturbing, twisted version of "Little Red Riding Hood". I dropped this early on but I plan on finishing it some other time. Not a big fan of the art. The gore is good tho, and the mc's messed up in the head so it ain't all bad. It's about a little girl's quest on finding "Mr. Wolf", whom she fantasizes on devouring her.
Murcielago
Exceptional in terms of gore. A bit explicit, has yuri 'scenes'. Not really scary? The MC is a psychopathic killer who agreed to work for the police and chase down criminals with her female partner/love interest.
The King and the Attendant