Iesada Tokugawa is the shogun of Japan, holding ultimate authority within the Tokugawa shogunate. He is pale-skinned with dark hair and red eyes that signal his unstable mental condition. Prone to psychological instability, he frequently locks himself away, muttering the phrase "Murasamemaru, murasamemaru, murasamemaru... I will drive out the imposters" as a mantra. This reflects a deep-seated paranoia and an obsession with proving himself as the only legitimate entity, driven by a fear of counterfeit beings.

He places a substantial bounty on the fuse, half-human, half-dog hybrids, fearing his status cannot protect him from their attacks. This decree initiates the main plot of the hunt. Iesada wields a sword with a blade made of water and a hilt and sheath constructed from bones, symbolizing his unusual and fearsome authority.

After a confrontation with the fuse named Shino, Iesada suffers a severe breakdown. He is reduced to a gibbering, thumb-sucking mess, sobbing incoherently and completely losing his grip on sanity. This collapse ends his active role in the narrative.

The character is loosely inspired by the historical thirteenth shogun of the Tokugawa shogunate, who ruled from 1853 to 1858, a period marked by the arrival of Western Black Ships and political upheaval. Iesada's characterization and the fuse panic echo the period's fears surrounding foreign influences and the weakening shogunate's fragility.