Ginshu serves as the 28th High Priestess of the Sakigami shrine, though his true purpose is to act as a decoy for the real Holy Princess, Shinshu. Originally, he was a boy named Ayame who was taken in and raised by an elderly woman before being called to serve at the shrine. Because of shrine tradition, despite being born male, Ginshu lives as female, dressing in heavy priestess robes and being referred to as a princess. After being cursed, his body became genderless and ageless, covered in dry snake-like scales as a physical reminder of his transformation.

At his core, Ginshu is a dedicated protector who loves Shinshu like a younger sister, baking treats for her and spending as much time playing with her as his duties allow. On the surface, he presents as charming, friendly, and remarkably shameless, with a sense of humor that allows him to laugh easily at situations that would embarrass others. He has a commanding presence and a way of making people listen to him and agree with his views, a skill likely honed through his training as a holy figure. However, this cheerful exterior conceals a deeply cunning and calculating mind. Beneath his gentle demeanor, he is always planning and preparing for the dangers inherent to his role, having been trained from a young age to understand the weight of his position as a decoy.

The defining tragedy of Ginshu's existence is his curse. After a disastrous confrontation with the snake demon Byakuroku, Bonten sealed Ginshu's soul into the demon's dead body to preserve his life, but the body rejects his soul. As a result, Ginshu dies and is reborn every single day, experiencing the pain of death in a never-ending cycle that he has grown to deeply resent. He hates having eternal life and genuinely wishes to find a permanent death. This torment has made him bitter, though he largely keeps his despair hidden from those who depend on him, choosing instead to maintain a bright disposition for their sake. The guilt he carries is immense, as he blames his own selfish curiosity and neglect for the series of events that led to the curse and the destruction of his relationships.

Ginshu's motivations are driven by his desire to escape his cursed existence and defy the will of Teiten, the entity that controls fate, known as Heaven's Net. His meeting with the demon Byakuroku opened his mind to question the fundamental differences between humans and demons, shattering the innocence he had been raised within. This quest for truth and his longing to change what has been preordained leads him to seek out Tokidoki, who is known as the Unwritten Page and possesses the power to alter fate. Ginshu asks Toki to side with him in his rebellion against heaven, hoping to finally find peace in death and save the people he cares about from the cruel destiny he believes awaits them.

Ginshu's key relationships are central to his story. His bond with Shinshu, the real Holy Princess, is one of deep, sibling-like love. He was willing to give his life to protect her, and she calls him big brother despite his official role. His other crucial relationship is with Bonten. They formed a secret, taboo friendship when Bonten was a young demon who breached the shrine's barrier, and despite being natural enemies, they grew close, playing games and questioning the boundaries between their kinds. The tragedy of the curse ruined their relationship, and though the warmth between them is gone, Ginshu cannot fully cut Bonten out of his life, continuing to allow him through the shrine's barriers so they can talk, still holding onto a fragile connection.

Throughout the story, Ginshu develops from an obedient young man who accepted his role as a decoy into a rebellious figure determined to go against his own fate and the fate of the world. He was once content simply to protect Shinshu and serve the shrine, but his forbidden friendship and the subsequent curse transformed him into someone who schemes against the heavens themselves. Rather than remain passive, he actively seeks the power to rewrite destiny, believing that the end Shinshu has foreseen will not be in their favor.

Ginshu possesses several notable abilities. His blood is poisonous to demons, causing any demon who bites him to die. He can detach his soul from his body and transfer it to another vessel, such as a doll, while his physical form rejuvenates. Beyond these supernatural traits, he is highly cunning and well-educated, skilled in calligraphy, reading, writing, and even baking, though the latter is considered beneath his station.