The whole world was ruined due to huge, tall, big monsters which most of them were like giant scary white rabbits with red eyes. Only a few sections like 1 or 2 in Japan were around with a very great protection system and survivors which they kept in that place.Yet in the biggest building,it was for high ranks,the heroes who would put their lifes in line to go out of safe zone to kill them. Each section in the whole outside based on its danger was ranked from A to F. The F was the worst..