Isaka lived as a wealthy human, indulging in extravagance and material possessions. He harbored deep despair over their inevitable loss after death, fueling existential boredom in his old age. To alleviate this boredom, he sought sadistic entertainment, watching people torn apart by wild animals within cages. His human life ended violently when Hokuto and Hazama killed him. Following death, Isaka reanimated as a shikabane and joined the Shichisei, an elite group of powerful undead antagonists. As a Shichisei member, he primarily utilized defensive supernatural abilities, specializing in creating impenetrable barrier cubes for protection; he took immense pride in these barriers, considering them unbreakable. In combat, Isaka could also open portals, though his role emphasized strategic defense over direct confrontation. His fate diverges between adaptations: the anime depicts him overwhelmed and killed when multiple shikabane himes breached his barriers simultaneously, while the manga shows his demise after a direct one-on-one duel with Makina Hoshimura. Throughout his existence as a shikabane, Isaka maintained a calculating demeanor, prioritizing self-preservation and leveraging his abilities to reinforce his perceived invulnerability. His backstory underscores themes of nihilism and the consequences of earthly attachments transforming into supernatural obsessions.