Hyoe Isurugi leads as the 26th head of the Isurugi ninja clan, dedicated to preserving its traditions and legacy. He rigorously trains his granddaughter, Rikka Isurugi, emphasizing mastery of ninja techniques and adherence to clan values, a path contrasting with Rikka's desire to follow her father Allen's scientific pursuits.

When assailants attack their home seeking Allen Isurugi's research, Hyoe confronts the invaders to protect his family. He sustains fatal injuries defending Allen, enabling Rikka's escape with the aid of robotic animal drones. His death in this confrontation hardens Rikka's resolve for vengeance.

The live-action spin-off *BLACKFOX: Age of the Ninja* features a feudal-era ancestor also named Hyoe Isurugi, commanding a mercenary group known as the Foxes. He initially agrees to protect Miya, a girl possessing electrical manipulation abilities, from the Negoroshu clan. However, accepting a rival offer, he betrays Miya, delivering her to the antagonists. This choice sparks conflict with his granddaughter Rikka, who believes commitments should outweigh financial incentives.

This ancestral Hyoe faces consequences for his moral compromise, fostering a rift within his group and spurring Rikka's independent mission to rescue Miya. His actions highlight recurring themes of duty, loyalty, and the consequences of choices within the Isurugi lineage across different eras.