There's a hunter that rank is e rank healer but he's healing power was not enough to heal any wound and he called the "useless healer",and one day he got betrayed by he's team raid and got stock in dungeon in 6 years and when he that he was going to die in the dungeon, he has discovered the other dungeon that who gave him a power, after he locked in dungeon for six year's he find a way to get out of dungeon and get revenge of the people cause of his incident.