Deadly Zero HP

A young man finds himself inside a forest with his face, and only just the face, turned into a skull.

He also figured out that his HP is 0.

But after the first fight with a Goblin, he figured out how to use Karma to shoot the damage back to the owner with the exact same amount, ignoring all armor.

An Immortal person with a masochistic, and at the same time sadistic, skill...what\'s going to happen next???

Update: Harem tag and comedy tag removed. That doesn\'t mean the humor is completely lost though, I just can\'t guarantee that my kind of humor would make you smile...