The Door in the Scar

The scar at the corner of his left eye is a door. Behind it lies a secret from three hundred years ago. Six pieces of iron, six worlds. Every piece he finds opens the door a little wider. But the door cannot stay open forever. Leave it open too long, and a person becomes the door. He has forgotten who he is. But he remembers that he owes someone an apology. That person lies on a stone platform in the Demon Realm, waiting for three hundred years. He does not know how to give it.