Jiku, also known as Jikū Ajari, serves as master and mentor to the protagonist Kujaku. Entrusted with Kujaku's care by the protagonist's father, this responsibility reflects deep trust. As an elder priest in the secret demon-hunting organization Ura-Kōya, Jiku wields considerable wisdom and spiritual knowledge. He guides Kujaku in harnessing supernatural abilities and confronting occult threats. Despite his respected position, he exhibits traits like alcoholism and perversion, mirroring some of Kujaku's less disciplined tendencies and adding complexity to his character.

He actively opposes antagonistic forces, including the Rikudoshu and the Teachers of Eight Leaves. These groups seek to revive dark entities such as the Peacock King and Snake Queen to create the Dark Vairocana. Jiku's leadership within Ura-Kōya positions him as a strategic figure coordinating efforts to thwart these apocalyptic plans. In live-action adaptations, his involvement extends to confronting modern threats. This includes collaborating with international allies like Tibetan lamas and Chinese spiritualists to oppose Nazi factions seeking ancient artifacts such as the dragon orb for world domination.

Jiku's background connects to Kujaku's family history through his intimate knowledge of Kujaku's father. This relationship underscores his protective role and contextualizes his commitment to guiding Kujaku through the challenges of his destiny. His character meets a definitive end in the manga continuity, killed by the demon Hōō. This death marks a pivotal narrative moment, highlighting the risks inherent in their ongoing battle against supernatural evils.