Haruka Luciela is an investigator for the Department of Anomalous Crimes Chemistry Division at the International Anomalous Tactics Organization, or IATO, an agency dedicated to tracking paranormal crimes linked to extradimensional entities known as "gods" and higher dimensions. Her primary work involves studying the Nights, mysterious lifeforms from other dimensions that negatively consume human souls, gathering intelligence on their activities and motives.

Assigned to assist the Kamaya City police department, she collaborates directly with the investigative unit led by Shingo Sumeragi. Haruka quickly notices the connection between Matoi Sumeragi's sudden exorcism abilities and the Tenman Shrine where Matoi works. Her methods prioritize obtaining leads by any necessary means, which leads her to deliberately establish close contact with Matoi and her best friend, Yuma Kusanagi, in order to further immerse herself in researching the multi-dimensional conflict. Despite her highly secretive approach to her work as an agent, she displays notable patience and kindness toward Matoi and Yuma, often adopting a protective stance with them.

Haruka has a distinctive appearance, featuring multicolored hair and green eyes. She is rarely seen without her signature cool shades. She wears an extremely low-cut top that frequently draws attention, contributing to her portrayal as a visual focal point and a notable example of fanservice within the series. Her demeanor remains professional and largely disinterested in romantic advances, despite receiving attention from male colleagues such as Hideo Tezuka. She is French, with her birthday documented as July 31, though her specific age is not provided in official sources.