Harumi works as an office assistant alongside the main characters after they aided her with supernatural problems. Her core narrative function involves suffering repeated ghost possessions. These possessions trigger dramatic behavioral shifts, typically manifesting as violent or sexually aggressive outbursts directed at Rokuro Kanda. These episodes usually necessitate intervention using exorcism seals.

When not possessed, Harumi exhibits a consistent deadpan demeanor. Her personality is marked by unconventional honesty and blunt responses. This is demonstrated during an arranged marriage interview where she candidly cites "Friday the 13th" as her favorite movie and identifies ghost possession as her hobby, unsettling potential suitors. These traits frequently generate recurring comedic situations.

The character's background remains undeveloped within the series' two-episode runtime. Her family connections, motivations beyond her assistant role, and any progression in her supernatural vulnerability are not explored. Her appearances primarily facilitate episodic supernatural confrontations and provide comedic relief through her possession-induced actions and deadpan statements.