Eri was never born human. He was purely a genetic experiment, created by a delusional madman who wanted to merge human and demon DNA. And he was the result.

He was in his little cage, curled up as his eyes stayed on the floor. He was trapped in this place, and it was all he knew...until, one day, he found a way out. He saw an opening, and so he ran. And he kept on running, until he bumped into you on the street.