A pure blood demon that raped and pillaged as he pleased. Three children were bore from him, and the middle child, Shanano, attacked Benkei at a young age in an attempt to kill him. Shanano was easily defeated by Benkei though, after his sword drew blood from the demon's forehead. Benkei, realizing the pain that he has caused, then attempted to commit suicide. A monk, by the name of Ajari, stoped the demon simply by telling him he is already dead. Benkei then decides to follow Ajari's teachings and sets out on the path for enlightenment.

A couple decades later, Benkei steals the Demon Slayer, and tells Ajari that Agaharia's revelation tells him to kill the two faced demon; Benkei then rushes off. He later confronts the demons on Gojoe bridge, but they flee to a cave in Kyoto. Benkei follows the demons to Kyoto but is trapped in the surrounding Devil's Woods by the Halfling Demons, and is then captured by the Heikei clan. The Heikei clan ask for Benkei's assistance in destroying the demons, but Benkei refuses.

Later the Heikei clan bounds Benkei and returns him to the Devil's Woods. Shortly afterwards the demons appear and kill the nearby soldiers of the Heikei clan, and Shanano fights Benkei and nearly kills him until Ajari shows up. Once again the Halfling Demons retreat to the caves in Kyoto.

Upon returning Shanano insists on putting Ajari's beliefs to the test by fasting for nine days. At the end of the nine days Shanano confronts Ajari and insists that he has reached enlightenment, and that all of Ajari's gods don't exist. Shanano then gets fete up with Ajari and kills him. The Halfling Demons then travel around killing all the monks that come across their path.

Benkei is then contacted by Shanano and is told that he has slain Ajari. Benkei decides to put behind his Buddhist beliefs and avenge Ajari. Benkei returns to Kyoto and meets the Halfling Demons on Gojoe bridge. Shanano fights Benkei one-on-one again, and greatly overpowers him until Benkei stabs himself in the forehead. Although Shanano quickly gains the upper-hand once more, and manages to stab Benkei in the stomach with his sword. Benkei is able to raise his sword to the sky as lightning hits it, killing them both.