Tsukasa Shishiou, dubbed the "Strongest High School Primate," first appears as a ruthless visionary intent on forging a new humanity in a shattered world. Shaped by a brutal childhood defined by relentless combat training to shield his terminally ill sister, Mirai, his early life as a martial artist fueled both her medical care and his growing contempt for a society that failed to save her. Revived millennia later into a petrified world, he spurns its reconstruction, branding it irredeemable. He founds the Empire of Might, reviving only youths he deems morally uncorrupted while obliterating statues of adults and perceived threats. Hostages like Yuzuriha become pawns to manipulate Senku, sparking violent clashes with the Kingdom of Science to suppress technological rebirth. Unmatched in raw power, Tsukasa slays lions bare-handed, snatches arrows mid-air, and topples trees with primitive weapons. Yet beneath his warrior exterior lies tactical cunning: he memorizes intricate chemical formulas, anticipates Senku’s strategies, and justifies his crusade against science as a safeguard against humanity’s self-destruction—even if it demands Senku’s death. A turning point arises when Senku offers to revive and cure Mirai through petrification. Her recovery fractures Tsukasa’s dogma, compelling him to join forces with his former enemy. He intercepts an assassination attempt on Mirai, suffering mortal wounds, only to be preserved cryogenically and later healed via petrification. Reborn, he abandons his empire, pledging loyalty to Senku’s scientific endeavors while vigilantly guarding against the societal decay he once sought to eradicate. Though ruthless, Tsukasa spares foes like Chrome and Gen, revealing a grudging code of honor. His rivalry with Senku evolves into mutual respect, cementing his shift from tyrant to ally—a transformation driven by devotion to Mirai and a rekindled belief in science’s capacity to redeem rather than ruin.