Holder of the Integrity bead. Genpachi is a captain of the imperial military police. Like his foster brother Kobungo, Genpachi was sent on assignment in the north three years ago and returned a changed man. Now he transforms into a demon who preys on supernatural beings.

He and Kobungo's sister Nui were once lovers, but when he was away for work with Kobungo, they were trying to save the emperor's daughter, but demons appeared and everyone died, including Kobungo and Genpachi.

However, they went back to life, now hald-demons and returned home. But everyone, including Nui, thought they were dead. So Nui got pregnant with a child from another man and when she learned that Genpachi was sound and safe and was going back, she couldn't handle the shame and threw herself into the river, killing herself and the unborn baby.

To protect Genpachi, Kobungo and others told him she passed away from a desease.

Unable to cope with Nui's death, Genpachi tried to commit suicide over and over until he realized he couldn't die, because his wounds would immediately heal. So he and Kobungo came to realize what happened to them.

Later on, Genpachi learns the truth about Nui from the priest but tells Kobungo he's not angry neither at him nor at Nui.

Genpachi seems to have an obsession with Shino which serves as a comic relief in the series, while in truth, Genpachi hasn't been seen with a woman after Nui died.

While staying at Genpachi's house, Asakeno mocks Genpachi for not bringing any women to his house, saying that he still seems to be clinging onto the dead which angers Genpachi and makes him point out to Asakeno that he's not as kind-hearted as others making Asakeno pursue the subject no further.
Stupidly obsessed with Shino at times, Genpachi seems to be one of the most perceptive ones, understanding how difficult it is for Shino and Sousuke to live the life they're living now, making him look more adult than others.

Genpachi's also very popular with women of any age, however he doesn't seem to be interested in any of them.

The staff at his house seems to be rather fond of him, including his old butler.