Reiji Senda leads the Shinjuku Ward Nocturnal Community Relations Division, mediating between humans and supernatural entities called Anothers. Born into a family with deep occult connections spanning generations of psychic mediums, he initially lacked the innate ability to perceive Anothers. Through persistent use of specialized occult tools, he developed sufficient sight to perform his duties effectively.

At 37, his leadership style is lackadaisical yet approachable, fostering a cooperative and efficient work environment. He possesses ochre hair and brown eyes.

A dedicated OVA, "Fukurokouji to Anoko to Ore to," details his first encounter with Theo Himezuka 15 years prior. At a temple, an unseen kitsune spirit clung to Reiji's back, trapping him. Theo, who could see Anothers, guided him to retrieve a buried box, prompting the kitsune's departure. This collaboration began their long-term partnership and eventual joint enlistment in the Division.

Reiji demonstrates protective leadership, notably in episode 11 where he intervened politically to shield his subordinate Arata Miyako from the antagonistic Satoru Kanoichi of the Tokyo Metropolitan branch. He strategically negotiated jurisdiction over a crisis involving the kaikogami (a silkworm patron goddess) to ensure Arata's safety and involvement in the resolution.