The Priestess, also referred to as Miko, is the leader of the Werebeasts and the ruler of the Eastern Union. Her current name appears in brackets because she lost her real name long ago, forfeiting it as a wager during the founding of her nation. Despite her considerable true age, she retains the appearance of a woman in her twenties, with long golden hair, fox ears, and two golden tails, and she typically dresses in a kimono and wears a monocle. She carries the title of shrine priestess because, as a child, she played a game with an ancient god named Holou and made a pledge that resulted in that god residing within her ever since.

In personality, the Priestess is calm, confident, and highly knowledgeable, and she wears a composed smile in nearly all situations. She is deeply affectionate and protective toward her own people, which is evident when she asks Sora to take care of the Werebeasts should she lose her wager against him. Her primary motivation is the prosperity and survival of her people, and she is willing to risk even herself to secure that outcome. This devotion to her nation is also reflected in her greatest strategic achievement: the Eastern Union originally possessed no territory on the continent, and she engineered a game that could not be lost, which allowed her people to claim land and grow into a powerful nation.

Within the story, the Priestess initially appears as a distant and formidable authority behind the Eastern Union's strength, and she looks down on Imanity at first. When Sora and Shiro confront her, she treats their challenge with amusement and condescension, but the outcome of their wager changes her perspective. After forming a truce with Sora and joining the Elchea Federation, she begins to place genuine faith in the siblings. Her trust is demonstrated through her decision to order Izuna and Ino to follow Sora and Shiro, believing that both of them can learn more from the siblings than they could under her own tutelage.

Her key relationships center on the siblings, her subordinates, and the god she carries. Her bond with Sora and Shiro develops from rivalry into trust and alliance, while Izuna and Ino act as her trusted agents whom she entrusts to the siblings' care. Her connection to Holou defines her spiritual role, making her both a political ruler and a vessel for a divine being. In terms of notable abilities, she possesses extraordinary strategic intelligence capable of constructing unbeatable games, a lifespan and vitality that preserve her youthful appearance despite her true age, and an enduring spiritual link to the god within her, a role that has shaped her entire life and leadership.