In a tranquil existence with his grandfather, seventeen-year-old Jirou Azuma taps into his unique gift of conversing with animals, forging protective bonds with them. Descended from a revered shinobi lineage, both Jirou and his grandfather hone their combat skills to uphold their family's martial traditions. Jirou's world is upended when he saves a stray black cat, Ragou, only to unveil its true identity as a mononoke—a malevolent spirit locked in a timeless conflict with humanity. When a vengeful mononoke targets Ragou, Jirou employs his shinobi training to defend the feline, enduring a fatal blow in the process. Faced with a critical choice to consume Jirou's waning life force for strength, Ragou selflessly transfers his energy to the youth instead. Resurrected, Jirou gains supernatural abilities that seamlessly blend with his shinobi prowess. This transformative act captures the attention of Ryousuke Shiba, an operative from the Bureau of Espionage tasked with neutralizing hostile mononoke. Impressed by Jirou's newfound powers, Shiba offers him and his grandfather a proposition: to enlist in Black Torch, the Bureau's elite unit dedicated to combating monstrous mononoke preying on the innocent.