**I have already finished reading this manga**

First off, if you are just looking for a happy-go-around romance/slice of life manga, stay the fuck away from this one. Saiteihen no Otoko is noticeably different from the majority of other manga because it actually tries* to be a true horror story, with very messed up contents that might just appeal to horror thriller fans. This is quite rarely seen in the medium of manga and anime.

For something that is only 3 volumes long, there are a tons of narrative contents told. The pages are filled with twists and turns, leaving readers on the edge of their seats. The manga never loses its intensity, though there is a clear departure of tone in the second half of story, opting for a less scary but more “shounen” tone. Compared to numerous other mystery manga that I have read (with shitty ending), it actually gives a great finish. Not masterpiece, mind, but quite good. At least I found it satisfying.

Being a psychological horror story, there is a heavy focus on MC’s (unstable) state of mind. The MC's 'loser' characteristic is vastly exaggerated. Still, it’s entertaining (in a shounen way) to see how even a person who resides at the bottom of social hierarchy can exhibit moments of heroism, at crucial moments.

The art is hit or miss, depending on whether you like drawings of messed-up faces in this mangaka's unique style. Regardless of your preference, the artwork contributes to the horror suspense atmosphere perfectly.

tl;dr

Overall, for its on a whole satisfying story, unique art style, and an interesting MC loser-kun, I award it with 8/10.

For ultimate recommendation, I point you to Ibitsu, also a short horror story.