Yo Uei was a police officer before the petrification event, his career marred by controversy due to his habit of shooting fleeing suspects, which threatened his future. He was petrified while urinating against a wall. Revived by Tsukasa Shishio, Yo joined the Empire of Might as an enforcer. During the Stone Wars, he guarded Chrome but failed to stop his escape. Fearing punishment, Yo faked his death and fled the empire, ordering subordinates to report him dead. While hiding near Ishigami Village, he encountered Homura and freed her after she promised benefits. Discovering Tsukasa's empire had merged with the Kingdom of Science, Yo falsely claimed amnesia to join them, assisting Yuzuriha in statue repair as redemption. Yo frequently argued with Magma over modern versus primitive methods. He participated in Kingdom projects like shipbuilding contests, hot air balloon construction, and farming. His competitive streak emerged during agricultural work when motivated by profits from the new currency. During the Treasure Island expedition, Kirisame petrified Yo and dumped him into the ocean. Retrieved and revived to operate a firearm due to his experience, he initially struggled with accuracy but improved through practice. Gen flattered him by suggesting he could become the Stone World's sheriff, securing his compliance. In battle, Yo shot the petrification device from Ibara's hand before being petrified again. In the New America City arc, Yo threatened the revived Tsukasa with his gun, though tensions eased as new threats arose. He gambled enthusiastically during the voyage, lost money to Ginro, and repeatedly complained about the lack of alcohol until beer was recreated. He later drunkenly recounted his confrontation with Ibara. Upon reaching America, he joined the warrior team escorting explorers and expressed excitement at hunting alligators for meat. During an aerial attack, he futilely shot at an enemy plane despite Hyoga's objections. Stanley's forces later subdued Yo, and he remained in Corn City with part of the team. In South America, Yo initially doubted diamond synthesis but became deeply invested in the process. He joined the fight for the petrification device and continued advancing despite being shot in the torso during the activation attempt, trusting petrification would heal him. He was ultimately petrified during Joel's activation of the Why-man's signal. After nine years in the Globetrotting arc, Yo revived in Corn City and participated in creating a computer. He voiced frustration over the labor but was motivated by a monetary prize for a math contest. He later helped deliver corn and the petrification device to Senku's team in Australia, engaged in rice farming in Indonesia without complaint due to personal interest, and expressed approval of dam construction efforts back in Japan. He fed Suika's pets, influencing their decision to stay, and attended the village feast. During the Moon Mission arc, he was petrified again when the device activated unexpectedly. Personality-wise, Yo displayed arrogance, cowardice, and laziness, often avoiding work unless incentivized by power or profit. He looked down on pre-petrification humans and mocked their lack of scientific understanding. Despite these flaws, he demonstrated loyalty to the Kingdom of Science after joining, showed concern for subordinates by taking blame for failures, and expressed genuine awe at Senku's inventions. His skills included police combat training, proficiency with tonfas and firearms, running speed, and tactical assessments. Physical attributes included a lean muscular build, spiky auburn hair, and a recurring stone eyepatch over his right eye. Post-revival outfits featured Kingdom of Science insignia. Statistically, his abilities were rated as Power 3/5, Speed 4/5, Technique 5/5, and Reach 1/5 according to Volume 9 data.