Nikkō serves as the Head Priest of Ura-Kōya, leading its secret organization devoted to demon hunting and exorcism. He approaches his duties with seriousness and discipline, a demeanor distinct from the unconventional methods of members like Kujaku. As leader, he coordinates operations against supernatural threats and safeguards the organization's spiritual integrity. His guardian deity, Mahāvairocana (Dainichi Nyorai), signifies his elevated spiritual rank and authority within Ura-Kōya. Nikkō acts as Kujaku's senior (senpai), offering guidance and oversight during missions. He appears consistently throughout the OVAs, functioning as a stabilizing presence. His personal background, origins, and character development remain undocumented. His responsibilities center strictly on organizational leadership and spiritual oversight.