Where did you read it?
Online, I don't remember the site.
Art Style?
Japanese Manga
Manga & Anime?
I don't know for sure but I don't think it has a anime adaption, there shouldn't be enough chapters.
Characters
MC was probably an early Adult. I think one of his friends was a Labia that died later.
Fantasy creatures?
There were demi-humans, I can't remember the monsters.
Target Audience?
Probably Seinen, there were some more graphic scenes.
Genre?
I assume Fantasy, Seinen, Action
In the beginning he was held captive in some facility and experimented on.
He had to fight there on a regular basis until he escaped.