>>84097699He has the blood of the dragon within him. If he uses his blood to heal you, you can not die. However, you suck the life from other living beings around you, a phenomenon referred to as Dragonrot.
There are other ways to become immortal, like drinking from the fountain, but then you get infested with centipedes like the monks and the monkey. Genichiro has cursed himself through the fountain too, and is imperfectly immortal.
