Hiraga Gengai, a brilliant yet accident-prone mechanic and inventor, crafts ingenious machines frequently derailed by overlooked flaws in their programming. His rugged appearance—industrial goggles perched atop a nearly bald head, a scraggly grey beard, and a gap-toothed grin—hints at a life spent tinkering in workshops. The death of his son, Saburou, who perished in the Joui War to halt Gengai’s weapon production, left enduring grief, exploited by manipulative foes like Takasugi Shinsuke to lure him into targeting the Shogun’s festival. Allies later steer him from vengeance, though the scars linger. Operating Machine Hall, a bustling repair hub, Gengai mends everything from battered scooters to damaged allies, including rebuilding the android Tama with scavenged parts and retrofitting Sacchan’s glasses into lethal tools. His mechanical armies bolster comrades against yakuza onslaughts during the Kabukicho Four Devas clash, while the Silver Soul Arc sees him engineer the Neo Armstrong Cyclone Jet Armstrong Cannon—nanomachine-laden artillery that cripples enemy tech but costs him freedom until rescue. Prone to reckless innovation, he repurposes mundane items into hazards and obsessively infuses soy sauce into gadgets like Kagura’s umbrella. His creations, from the son-inspired robot Saburou to the ally-commissioned Kintoki, blur lines between genius and chaos. Inspired by the historical polymath Hiraga Gennai, his narrative role mirrors the Edo inventor’s eclectic legacy. Loyal to friends, he risks his life alongside them, valuing human bonds over mechanical utility, even as his inventions spiral into bedlam.