Kaguya is a princess who appears in Garo: Crimson Moon, distinguished by her mysterious origins and otherworldly nature. She was found as an infant inside a bamboo stalk by an elderly couple who raised her as their own daughter. This origin directly references the classic Japanese folktale of The Tale of the Bamboo Cutter, setting her apart from many other characters in the series who are based on historical figures. For a time, she lived a quiet life, but her mysterious circumstances eventually drew unwanted attention.

In terms of personality, Kaguya is portrayed as a gentle and somewhat melancholic figure. She possesses a quiet dignity and a deep sense of gratitude, particularly toward her foster parents, whose love was the primary reason she chose to remain on Earth. Despite her incredible power, she is not aggressive or arrogant. Instead, her motivations are rooted in emotional bonds and a sense of duty. Initially, her only desire is to be with her family, but after their tragic loss, she finds a new purpose in helping those who fight against the Horrors.

Kaguya’s role in the story evolves significantly. At first, she is a passive figure, a princess with many suitors who are mysteriously killed. It is believed she might be a Horror herself, but the truth is that her foster parents, corrupted by greed, became hosts to Horrors. They demanded impossible treasures from her suitors, and when the suitors failed, the Horrors within the parents would kill them. After Raikou, the protagonist and a Makai Knight, slays the corrupted parents, Kaguya loses her reason to stay on Earth and returns to the moon. However, she later returns when the moon turns crimson due to the schemes of the antagonists Ashiya Douman and Priest Douma. Her return reveals her true nature and her crucial role in the climactic battle.

Her key relationships are central to her character. Her bond with her foster parents, despite their fatal flaws, is her primary anchor to humanity. After their deaths, she forms a significant connection with Raikou and the Makai Priest Abe no Haruaki. It is through Haruaki’s ritual and guidance that she begins to understand her true purpose. Kaguya’s most critical relationship, however, is with the monstrous entity Rudra. She was not born a normal human but is, in fact, a human-shaped Madōgu, a magical tool created long ago by the Abe clan specifically to seal away the ancient and immensely powerful Horror, Rudra. Her entire existence is tied to this purpose, and much of her development involves rediscovering this lost identity and the full scope of her abilities.

Throughout the series, Kaguya undergoes a process of self-discovery and empowerment. Initially having forgotten the extent of her power, she slowly remembers it piece by piece. Abe no Haruaki performs a ritual that helps her recover almost all of her strength, and later, with the help of a magic book from Fujiwara no Michinaga, she is able to recall all twelve lines of the incantation needed to seal Rudra. By the end of the story, she fully embraces her role, participating directly in the final confrontation against Rudra. After the Horror is sealed, she chooses to return to the moon once more, but this time she does so with a sense of peace, promising to watch over her friends and observe the progress of humanity.

Kaguya possesses several notable abilities, most of which are tied to her nature as a magical tool. She has a powerful healing ability, capable of mending wounds with just a gentle touch. She can also create magical barriers for protection. While these are her most commonly displayed abilities, it is suggested by Haruaki that she has the potential to be far more powerful. Her ultimate and most crucial ability is her connection to the sealing spell for Rudra, the ancient Horror. Without her knowledge of the twelve-line incantation, the monster could not be stopped. Her very being is her most powerful weapon, as she was the linchpin of the sealing performed by the Abe clan in ancient times.