Ratio is a Hamatora private investigator and medical professional holding a doctorate. He co-operates a handyman business with Birthday, his professional partner and childhood friend.

Ratio wields a Holder ability named fastidiousness. This power allows him to perceive the structural composition of a person's body and pinpoint their physiological weak points, activating when he removes the eyepatch covering his right eye. After identifying vulnerabilities, he employs brass knuckles to subdue opponents in close-range combat.

His partnership with Birthday encompasses both their shared business and collaborative investigative efforts within the Hamatora framework.