Tsukasa Shishio, a high school martial artist dubbed "The Strongest High School Primate," rose to prominence through an undefeated mixed martial arts career prior to humanity’s petrification. His lethal physical prowess enabled feats like killing a lion with a single strike and intercepting crossbow bolts mid-flight at 200 km/h, earning him renown even beyond combat sports enthusiasts. Driven by devotion to his comatose younger sister Mirai—whose traumatic brain injury resulted from adult abuse—he dedicated himself to funding her treatment. This tragedy cemented his disdain for authority and hierarchical systems, branding adults as inherently corrupt. Upon awakening in the petrified world, he sought to forge a society reviving only morally pure youths, systematically shattering adult statues to dismantle old societal foundations. Initially allying with Senku Ishigami’s group for survival, their partnership fractured when Tsukasa opposed restoring advanced technology, fearing its potential for exploitation. He spearheaded the Empire of Might, enlisting formidable allies like Hyoga and Homura, and targeted Senku to halt scientific resurgence. A truce formed when Senku proposed using petrification to heal Mirai, but Hyoga’s betrayal shattered this alliance, leaving Tsukasa mortally wounded. To preserve his life, Senku devised cryogenic suspension until petrification-based revival could mend his injuries. Post-revival, Tsukasa channeled his efforts into bolstering the Kingdom of Science, leveraging his combat mastery and tactical acumen in expeditions and clashes against militarized foes while upholding his vision of moral integrity. Towering at 195 cm with a muscular frame, Tsukasa’s wild chestnut-brown hair and stone-derived scars etched across his face and torso underscore his formidable presence. His attire transitioned from a lion-pelt cloak to utilitarian garments, mirroring his shift from solitary warrior to collaborative strategist. Despite his ruthless tactics, he upheld a strict code—eschewing resource waste and minimizing suffering in necessary kills. His relationship with Senku wove rivalry with mutual respect, their early interactions hinting at potential friendship under different circumstances. Post-revival, his loyalty pivoted to safeguarding innocents within Senku’s scientific realm, symbolizing a convergence of their once-opposing visions for humanity’s rebirth.