Gantz( Seinen)17+

Series Info
Title: Gantz
OM Rank: 14
Categories: action, anime, mature, seinen, supernatural
Author: Oku Hiroya

Artist: Oku Hiroya

Chapters: 277 - ongoing

Summary
Somewhere in Tokyo, there is a room. In that room is a black sphere. Periodically, people who should otherwise have died are transferred to the room. There, the sphere gives them special suits and weapons, and sends them out on a mission to kill aliens here on Earth. While these missions take place, the rest of the world is largely oblivious to them. These missions are lethal - few participants survive them. The sphere calls the shots, and it's not the slightest bit nice. It's name... Gantz.

Online view:
Gantz

How many chapter is this manga ?

i forgot, its not complete. its around 276.