Judas

Meet Judas, the spirit of death, is cursed for his sins and must reap 666 souls in order to get back his human body. Problem is, he's an Intangible Man, thus can't actually kill anyone. Thus he takes Eve, a trappish young boy, and possesses him to use his death powers and reap souls... Except it seems to get plenty sidetracked by people who are obsessed with 'Eden', and the inhumane acts they commit to find it...

...Much better than it sounds.

Tropes associated with this manga:

 * Awesome McCoolname: Judas? Awesome. Zero Equals Mascchettiano? Badass.
 * Body Horror: Paul. Oh god, Paul. Also, all the experiments Sorahito did or the results from being injected with the Eden drug in general.
 * Buried Alive:
 * Complete Monster:
 * Death Seeker: Mizuki, and once upon a time, Eve.
 * Friend to All Living Things: Kogiku
 * Gender Bender: Eve, when Judas is using his powers to reap.
 * Good Powers, Bad People:
 * Hospital Hottie: Mizuki counts as one.
 * Ill Girl: Kogiku
 * Mad Doctor: Attacking and injecting others with syringes? Yup, Hibiki.
 * The Problem with Fighting Death: Pretty much the reason why those obsessed with Eden go psycho.
 * Time Master: Philip
 * Time Master: Philip