Kakugo Hagakure, younger brother to Harara Hagakure, underwent rigorous combat training from early childhood under their father Oboro Hagakure. Prepared to battle monsters in post-apocalyptic Tokyo, this training focused on mastering the Zero Defense Form martial art and utilizing eight steel balls embedded within his body. Kakugo can absorb these balls to coat his skin in metal or eject them as projectiles. His signature combat technique is Impact, a countermove that redirects an opponent's attack energy back at them. He wields the prototype Fortified Armor Shell "Zero," forged by their grandfather Shiro Hagakure, a former Imperial Japanese Army scientist. This armor draws power from the souls of 3,000 deceased Japanese soldiers sacrificed during its creation. These souls form a collective consciousness that manifests as grimacing skulls, communicating tactical advice and warnings to Kakugo during battle. The sentient armor actively supports his missions, creating a symbiotic relationship despite its vengeful origins. Kakugo's moral compass prioritizes duty and protection, starkly contrasting with Harara's descent into villainy. He demonstrates compassion through actions like cremating fallen comrades and showing empathy toward the souls within his armor, even mutilating his own mental form to understand their suffering. His commitment to defending civilians leads him to attend Reverse Cross High School, strategically located near Harara's stronghold, where he confronts monsters and his brother's Tactical Fiends. Key relationships include his bond with classmate Tsumiko Horie, who develops affection for him after witnessing his heroism. When Chidokuro transforms Tsumiko into a Tactical Fiend, Kakugo fights to restore her humanity, ultimately succeeding through a kiss that breaks her monstrous form. His dynamic with his father Oboro is defined by loyalty; Kakugo continues their mission even after Oboro's death at Harara's hands. In later media, Kakugo reemerges in the sequel *Exoskull Zero* following a prolonged slumber. He encounters six other armored warriors, including Harara, who possess divergent approaches to justice. This new narrative unfolds conflicts within a world deteriorated further still.