Shiro Mibu manages Komugi Nakahara at the Kiri Pro talent agency. He generally maintains a relaxed attitude, which hardens when Komugi shirks her duties, usually for her magical nurse activities. During these absences, he covers her professional responsibilities, often donning her costumes. His frustration emerges through sarcastic comments and nicknames for Komugi like "Little Shit" or "Little piss-ant girl." Despite this contentious dynamic, he shows loyalty by defending her during reprimands from agency president Yui Kirihara.

Mibu possesses computer skills, designing and maintaining Komugi's official fan site. His tendency towards macho behavior and bluntness frequently causes problems, especially with Yui Kirihara, who scrutinizes his conduct. Physically, he has gray hair, brown eyes, a scar, and a smoking habit. His professional role and interpersonal conflicts remain consistent across his appearances in the original OVAs and the Magikarte Z sequel. Originating from The SoulTaker universe as a mysterious ally to Kyousuke Date, his parody iteration in Nurse Witch Komugi is a distinct comedic figure without shared narrative continuity.