A renegade man-beast, Amano has spent the past three hundred years scouring the planet for the Chōjin ("Super-Deity").
Due to his many misdeeds involving Mimi, daughter of the Elder, he is banished from the demonic realm and spends 300 years in the human world.
In actuality, the Elder sent Amano to find the Chōjin, a demonic god whose dormant spirit is sealed in the body of a human.
He is also shown to have no respect for human life, one example is during his first appearance when he tosses a baby he saved from an oncoming truck into a storm gutter to drown, wondering why he even bothered to help the infant at all.
During the final episode of the first OVA series, Amano desperately tries to appeal to Nagumo's human nature to no avail and sheds tears when he realizes that it is beyond his control.
As the series goes on, Amano's faith in the prophecy is challenged constantly and eventually resolves to put an end to the Chōjin and preserve the three worlds as they currently exist.