Yo Uei worked as a police officer before petrification, notorious for using excessive force—including shooting fleeing suspects—and expressing regret over his stunted career prospects. He was petrified while urinating on a wall. Revived by Tsukasa Shishio, he joined the Tsukasa Empire as an enforcer. During the Stone Wars, he guarded Chrome but failed to prevent his escape. Fearing punishment, he faked his death and fled, ordering subordinates to blame everything on him. He encountered Homura near Ishigami Village, freeing her in exchange for promised benefits. Discovering the Tsukasa Empire had merged with the Kingdom of Science, he feigned amnesia to infiltrate Senku's group. As penance, he assisted Yuzuriha in reconstructing petrified statues while complaining about the labor and worked in Taiju's farming division. His abrasive, arrogant, and cowardly personality led him to belittle post-petrification humans as savages. Self-serving and power-hungry yet unintelligent, he was easily manipulated by Senku and Gen. Despite this, he showed flickers of loyalty by shielding subordinates and committing to statue repair for redemption. Lean and muscular with spiky auburn hair, Yo typically wore a sleeveless grey yukata. A stone fragment persistently covered his right eye across multiple revivals. His stats emphasized technique and speed over power and reach. As a former officer, he wielded police combat skills, specializing in tonfa and firearms. Though initially rusty with guns, he regained marksmanship through practice, leading the Kingdom to entrust him with their first firearm during the Treasure Island Arc. In the Age of Exploration Arc, Yo competed in shipbuilding but produced only a rudimentary raft. He envied Ryusui Nanami's lifestyle and reluctantly engaged in new economic systems. During hot air balloon construction, he clashed repeatedly with Magma over modern versus primitive human capabilities, though both marveled at the completed balloon. For farming, Gen manipulated Yo and Magma into a competition that boosted crop yields after adopting Senku's soil-enhancement methods. On Treasure Island, Kirisame petrified Yo and dumped him into the ocean. Revived, he fired at Moz but missed. He later shot the petrification device from Ibara's hand, only to be petrified by Ibara immediately after. Taiju revived him underwater. In the New America City Arc, he nervously aimed his gun at the revived Tsukasa but stood down after Tsukasa assured cooperation. He gambled extensively during the voyage and complained about the lack of alcohol until beer was recreated. Joining the warrior team in America, he hunted alligators for meat and fired uselessly at an enemy aircraft. During the South America Arc, Yo participated in diamond synthesis, initially skeptical but later boasting about newfound wealth. In the fight for the petrification device, he urged Magma to activate it and was shot in the torso. Nikki encouraged him to continue, noting the injury would be non-fatal if petrification succeeded. He was petrified during the global petrification event. Nine years later, revived in Corn City, Yo joined the computer-building effort. He resisted the labor and mocked Ukyo's math contest but participated eagerly after Minami offered a cash prize. He transported corn and the petrification device to Senku's team in Australia and Indonesia, assisting in rice harvesting without complaint. Returning to Japan, he noted villagers industriously building a dam. He fed Suika's pets and attended a village feast before being petrified again alongside Gen during the Moon Mission Arc.