Yo Uei is a pre-petrification human and former policeman. Originally a member of the Tsukasa Empire, he faked his death after Chrome's escape to avoid the blame, then eventually joins the Kingdom of Science after the stone wars are over. As penance, he worked with Yuzuriha to rebuild the statues that were destroyed by Tsukasa. Yo also worked in the farming division under Taiju. However, he is constantly butting heads with Magma due to each other's naivety in their respective worlds. Yo is a lean but muscular young man of slightly above-average height with incredibly spiky auburn hair, left to flow wildly behind his head. He has a massive piece of stone covering his right eye. For some inexplicable reason, despite ditching the stone eyepatch several times, it somehow always makes a reappearance. Following his fifth petrification, his hair has been rendered shorter due to pieces breaking off in the process. He typically wears a short, grey sleeveless yukata that leave most of his legs exposed. He has a very large shoulder pad on his left shoulder and wears a spiked necklace. Like many in Tsukasa's Empire, he goes barefoot, though he does decorate himself with ankle bracelets. When Yuzuriha builds a fashion store, Yo wears a modern outfit. Prior to the petrification, Yo wore a police officer uniform. He is first shown as being abrasive, rude, and arrogant, having shown off his skills in front of his subordinates to prove how strong he is. He believes himself to be on the same level as Tsukasa, Hyoga and Ukyo when he is little more than a strong-but-unintelligent, violent thug. He also has a tendency to look down on people, especially the Post-Petrification people. He laughs off Chrome's attempt at escape, believing that he was trying to rub two sticks together to create fire to burn his way out (in reality, Chrome was using a battery, but uses Yo's misconception and belittlement to his advantage by feigning ignorance). In addition, he frequently laughs at the "savages" (stone world humans) for not understanding modern science, such as laughing at Magma for looking down on modern science (Magma is the person he fights with the most). He can be rather dismissive, believing Senku to have gone nuts in chapter 96 when he starts building his GPS as he can't understand the science behind it. Despite this, he considers modern humans superior to "savages" and takes every chance he can get in proving this. He is a coward and, once Chrome managed to escape, is quick to leave the Tsukasa's army for fear of punishment. He goes so far as to feign amnesia to join Senku's Kingdom of Science since it would mean a greater chance of survival. He tries to butter up to them by claiming he would like to "redeem himself" by working for Yuzuriha in repairing the broken statues, though this works against him as it proves to be more work than he wished. He is shown to dislike work, often complaining about having to help Yuzuriha's statue fixing (a rather arduous task) and needlework. He similarly complains about farming, though he can be motivated when the promise of profit or power comes along. Even in his past, he was shown to often disregard rules, once shooting a suspect while claiming that it was because they were trying to flee, and similarly peeing on a wall while being petrified. He has also admitted to being trigger-happy, shooting people on sight. His abrasive, power-seeking personality also makes him easy to manipulate into doing Senku's and Gen's bidding. He often tries to butter up to his superiors while coveting power, though is mostly harmless due to his lack of intellect. He and Magma get into fights often about the capabilities of the "savages" and the capabilities of "modern people", along with their similar personalities, strength, and desire for power and leadership. Despite this, he does have at least one or two redeeming qualities. While fleeing, he tells his remaining subordinates to tell Tsukasa that he died and to put all the blame of Chrome's escape on him (though this would have no consequences on Yo himself since he would be thought dead, but also no benefit) implying that he at least somewhat cares about his subordinates. He is even willing to redeem himself by helping Yuzuriha out by rebuilding statues with her. Since allying with Senku, Yo is now a loyal member to the Kingdom of Science and while he still seeks power, Yo has not made any attempts to claim it. Indeed, he is often amazed by Senku's inventions and once stated he wished to meet him before the Petrification event.