Nigira is the leader of the Kōhamei sect and the younger brother of Kyōra. He bears a large scar across the right side of his face, making him nearly identical to his brother save for that mark. His background within the sect places him among the figures responsible for safeguarding the Beast Spear and determining who is worthy of wielding it.

Initially, Nigira is opposed to entrusting the Beast Spear to Ushio, skeptical of the young protagonist's capability. He is eventually persuaded by Oyakume to observe Ushio instead, using that observation as a means to test Ushio's worth. This cautious and traditionalist mindset defines his personality: he is a pragmatist who values proven strength and responsibility over impulsive trust. His motivations center on the protection of the sacred weapon and the proper continuation of the sect's centuries-old duty.

Within the story, Nigira serves as a gatekeeper figure, representing the established order that must be convinced before Ushio can fully assume his role. His relationship with Kyōra is one of kinship and shared authority, though the scar distinguishes them physically and may hint at past trials. His most significant interactions are with Oyakume, who guides him toward a more open approach, and with Ushio, whom he reluctantly agrees to evaluate.

Nigira experiences a measured development: he moves from outright opposition to conditional acceptance, and eventually to recognizing Ushio's worth through direct observation. While specific abilities are not detailed, as a sect leader he is presumed to possess knowledge of spiritual arts and combat relevant to the Kōhamei's mission. Nigira remains a supporting figure whose principal contribution is the test of character he imposes on Ushio.