Yū is a young male character with long black hair parted centrally, styled with a braided ponytail secured by a white ribbon and a distinctive upward-tilted strand at the crown. Two crossed plasters mark his forehead, and his outfit includes a black jacket adorned with pale buttons and collar-cross insignia, black trousers, and shoes. Beneath the jacket lies a blue sleeveless shirt featuring three white horizontal stripes and crisp white trim along the collar and torso. A large rucksack frequently accompanies him. Positioned as Vulcan Joseph’s self-declared apprentice, Yū fervently admires Vulcan’s mechanical expertise, aiding him by scavenging materials for inventions after corporate suppliers abandon the workshop. Driven by a resolve to master mechanics, he supports Vulcan despite resource shortages. In the VS. Special Fire Force Company 5 arc, Yū demonstrates bravery by shielding Shinra Kusakabe post-rescue from an Infernal, later confronting Company 5 members who detain Shinra—showcasing loyalty to allies. During the Vulcan’s Workshop arc, Yū orchestrates Shinra, Arthur Boyle, and Iris’s entry into Vulcan’s workshop, urging Vulcan to ally with Company 8. He discloses Vulcan’s familial exploitation by Haijima Industries, detailing how Vulcan’s grandfather and father became Infernals under Giovanni’s suspicious influence. This revelation cements Yū’s role as both confidant and moral anchor. When Giovanni attacks the workshop, Yū is strangled as coercion to seize the Key to Amaterasu. Surviving via Iris’s treatment, he later thanks Company 8 for their aid. Yū’s resilience is tested when Giovanni implants a mind-control bug, nearly subjugating him. Arthur Boyle destroys the parasite, freeing Yū and emphasizing his vulnerability amid ongoing dangers tied to Vulcan. In the Arthur’s Adventure arc, Yū joins Arthur, Vulcan, and Lisa Isaribi on a Netherworld expedition, prompted by a quest to rebuild Excalibur with orichalcum. His participation underscores his expanding role in high-stakes missions. Yū’s name (ユウ) holds potential kanji interpretations like “excellence,” “permanence,” or “bravery,” mirroring his tenacity. At 142 cm and 39 kg, his compact frame contrasts with his proactive spirit and unwavering commitment to Vulcan’s cause.