Rabbit Doubt

Rabbit doubt (or Doubt) by Yoshiki Tonogai is a horror manga that might not be for everyone. I first read this manga years ago on Onemanga.com I believe. I was sitting on the edge of my sit waiting for the next chapter to come out only to see my guess as to who the killer is was wrong each and every time.

The manga was first serialized in Square Enix's Monthly Shōnen Gangan on July 12, 2007 and ended its run on February 12, 2009. Square Enix also released the first volume on December 22, 2007 and released the fourth and final volume on February 12, 2009. The series has continued with a sequel, titled Judge. (Wiki) 

 I have not read the sequel personally only because I didn't know there was one until now.

Genres: Mystery, Horror, Psychological, Thriller

Summary:  

Doubt revolves around a fictional cell phone game called "Rabbit Doubt", in which the players are rabbits in a colony; one of these players is randomly chosen to act as a wolf infiltrating the group. Each round, the rabbits guess which is the wolf as the rabbits are eaten one-by-one until only the wolf is left.

In the story, four players of the "Rabbit Doubt" game Yū Aikawa, Eiji Hoshi, Haruka Akechi, Rei Hazama and a non-player Mitsuki Hōyama meet to relax together. They are knocked unconscious and awaken in an abandoned psychiatric hospital to meet Hajime Komaba and discover Rei hanged. The group find Rei's cell phone and realize that they're playing a real-life game of "Rabbit Doubt". To survive, the wolf, described as the liar, must die.

Picture found on Google*
Summary found on  Wikipedia*