Mammouth, named Umibozu in the original Japanese, recurs throughout the City Hunter franchise. His background as a mercenary and former commanding officer of protagonist Ryo Saeba in a guerrilla band established a foundation of rivalry and mutual respect. This later evolved into an uneasy alliance, complicated by conflicting loyalties rooted in Ryo's forced exposure to the Angel Dust drug under Umibozu's command. Physically imposing, Mammouth wields immense strength and combat proficiency, specializing in heavy weaponry and demolition tactics. He maintains meticulously prepared weapon caches strategically placed across Tokyo, enabling swift access to armaments like the Mk 153 SMAW rocket launcher and M60E3 machine gun during operations. Within narratives, Mammouth operates as both antagonist and ally. For example, pursuing the "Cupid's Perfume," he steals the macguffin, igniting conflict with Ryo. Later, he intervenes decisively at the climax, eliminating multiple henchmen to aid the outnumbered Ryo and Kaori. This pattern of shifting allegiances repeats in "City Hunter: Shinjuku Private Eyes," where he provides critical firepower support during the final drone battle against PMC forces, deploying his signature heavy weapons to destroy structures and overwhelm enemies. His relationship with Ryo remains complex, marked by underlying tension from their shared wartime trauma yet punctuated by moments of professional cooperation during high-stakes missions.