Parasyte: Random student forced into a hidden world with life and death battles while also pondering the right to exist
Deadman wonderland: student forced into life and death battle while trying to decide how he wants to evolve in mentality and ability to survive
Shiki: (humans vs vampires) are against each other and ponder the right to survive, gore, violence
Ajin: another poor sap finds out he's a being that humans don't think are worthy of humane treatment and ponders what his morality should be while also being unique in he does good stuff for not entirely innnocent reasons (honestly one of the most interesting protagonists I've seen in recent years)
Nabari no ou: for some odd reason i think this is one too, with a protagonist who wants nothing to do with the world he's brought into and has many different viewpoints thrown at him. not really survival but the protag is interesting. not really sure why but i reccomend it.
Btoom!: poor sap, crazy world, who does he want to be morality wise? survival.
