Jikū Ajari serves as the master and mentor to the protagonist Kujaku in the Saga of the Phoenix narrative. Entrusted with the care of Kujaku by the young man's father, this responsibility reflects a deep and abiding trust placed in him. As an elder priest within the secret demon-hunting organization known as Ura-Kōya, Jikū wields considerable wisdom and extensive spiritual knowledge, which he uses to guide his charge in harnessing supernatural abilities and confronting occult threats.

In terms of personality, Jikū presents a complex figure. Despite his respected position and considerable authority, he exhibits noticeable flaws such as a tendency toward alcoholism and perverse behavior. These traits mirror some of Kujaku's own less disciplined inclinations, adding a layer of complexity to his character and making him more than a stereotypical wise old master. His motivations are rooted in his duty as a protector and a strategist. He actively opposes antagonistic forces, including the Rikudoshu and the Teachers of Eight Leaves, groups that seek to revive dark entities such as the Peacock King and the Snake Queen to create the Dark Vairocana. His leadership within Ura-Kōya positions him as a key strategic figure who coordinates efforts to thwart these apocalyptic plans.

Within the story, Jikū's role is primarily that of a guide and coordinator. His background is intimately connected to Kujaku's family history through his close knowledge of Kujaku's father, which underscores his protective role and contextualizes his commitment to guiding Kujaku through the challenges of his destiny. This key relationship is the cornerstone of his narrative function, as he works to prepare Kujaku for the dangers ahead. In some adaptations, his involvement extends to confronting modern threats, such as collaborating with international allies like Tibetan lamas and Chinese spiritualists to oppose groups seeking ancient artifacts for world domination.

The character undergoes a significant and definitive development in the manga continuity, where he is killed by the demon Hōō. This death marks a pivotal narrative moment, highlighting the grave risks inherent in the ongoing battle against supernatural evils and serving as a major turning point for the story and for Kujaku's journey. Jikū's notable abilities stem from his position as a high-ranking priest, granting him considerable wisdom, spiritual knowledge, and the power to harness supernatural forces to combat occult threats.