Kafuin is the construct built in the Keep of the Five Worlds, centered around a flawed Jewel of Judgment, and drawing power from the elemental shadows that surround the Keep. He is in charge of the Elder Seal which closed off the Fount of Power and locks the Outsiders, well, out. He also maintains the environs of the Keep, and molds shadow and such when Shizumaru is not around to do so directly.

Kafuin manifests as a crotchety old monk of the Way of Light. Shizumaru decided to emplate him on Kafuin Nikochin, the late master of his own sensei, Haohmaru. Kafuin is a bit whimsical, at times, but takes his duties quite seriously.

Recently, Kafuin was zapped by the Gloom Device when it snatched Shizumaru to another universe; his attempts to fight it got his CPU fried and accidentally flung Rimururu to a random shadow. Nagisa has completed repairs on him, and he is now the same as ever.