Summary
A Major General of the Root Clan. Throughout the story, there are red treasure chests scattered across four countries, and opening them triggers a trap where a hundred demons attack the opener. (An event begins where the player must fight all 100 demons.) The Hyakki King is the final demon that emerges from the treasure chests.
A thousand years ago, when the Ihika Tribe was still allied with the Root Clan, they created this trap.