Gen'ai Hiraga is the Mobile Shinsengumi's resident inventor and scientist. He designs and builds gadgets, weapons, and technological devices to help the team capture unlicensed monsters threatening Kyoto. While a small number of his inventions work as intended, many malfunction spectacularly or prove hazardous, such as a monster-energy-powered digging machine prone to dangerous failure. He excels as an excellent cook.

Gen'ai exhibits a ruthless, morally ambiguous approach to testing, frequently subjecting the monster cat Nekomaru to involuntary experiments that cause painful or unpleasant results. When others fail to cooperate adequately with his demands or testing protocols, his demeanor shifts dramatically; his eyes take on an unnatural, eerie gleam and his voice acquires a demonic, rumbling quality. This transformation leads Nekomaru to declare that Gen'ai possesses monstrous qualities exceeding his own.

Visually, his character design strongly resembles Dr. Tofu from Rumiko Takahashi's *Ranma ½*, reflecting Takahashi's role as the original character designer.