Miroku Fujima holds the position of Interrogation Officer within the Spirit World Warriors Society. Initially presenting as a tall, slim man with brown hair, blue eyes, and small stubble, he typically wears green glasses, black leather gloves, a light-blue shirt with a bootlace tie, a gray coat, white pants, and often carries a juicebox of banana juice. His appearance later undergoes a drastic transformation; he dons a flowing grey robe with a hood, conceals his left eye with an eyepatch, and reveals severe corruption on the left side of his face and head, marked by glowing purple tentacles consuming his eye and burned, cracked skin.

He maintains a likable, calm, and smiling demeanor, a deliberate facade masking his true manipulative and deranged nature. Beneath this exterior lies a twisted obsession with youmu and a readiness to exploit others for his objectives. He harbors a specific fixation on Izumi Nase, remarking on her beauty and finding her intriguing, which evolves into a plan to merge with her via a shared youmu implant.

His background remains largely obscure, though he joined the Spirit World Warriors Society after operating independently, a move intended to further his own malicious goals. He implants a tentacle-like youmu into both his own eye and Izumi's, claiming it would enhance their understanding of youmu. This act later enables him to use the youmu as a conduit to seize control of Izumi's body.

During the advance of the Hollow Shadow, he manipulates unfolding events in Nagatsuki City, including gaining permission from the Nase family to monitor youmu movements. He engineers conflict by exploiting Sakura Inami's grief over her sister Yui's death, providing her a weapon that absorbs youmu essences. Though Sakura fails to eliminate Mirai Kuriyama, Miroku retrieves the weapon and its accumulated energy, attempting to unleash the youmu known as Beyond the Boundary. This plan is thwarted by collective efforts, but he destabilizes the Nase family by exposing Izumi's youmu infection.

After a confrontation, Izumi offers a merger through their shared youmu, allowing Miroku to take over her mind. For a year, he uses her body to spread parasitic youmu globally, killing Spirit World Warriors and transforming them into shadow creatures. He contacts the amnesiac Mirai under false pretenses, posing as a source of information about her Blood Clan lineage. This ruse aims to infect her with a youmu, triggering a rampage. When she resists, he impersonates Akihito Kanbara, attacks her apartment, infects her, and departs to let the youmu consume her.

His endgame unfolds in an abandoned atrium, where his physical body—already devoured and corroded by the youmu—is discovered as a dormant shell. A prerecorded message reveals his plan to plunge humanity into darkness, leaving only himself and Izumi conscious. After Izumi (under his control) is defeated and Mirai freed, his consciousness is expelled, neutralizing the youmu infection and ending his scheme.

His abilities include expert swordsmanship, demonstrated against Izumi Nase and Ayaka Shindou, and proficiency in hand-to-hand combat. He possesses specialized knowledge as a youmu surgeon, enabling him to implant and manipulate youmu. His signature weapon absorbs youmu essences, growing stronger with each defeat.

Personal details include a January 8 birthday, Capricorn zodiac sign, blood type A, and a height of 1.80 meters.