She was close friends with Marisa and Guest. At age fifteen, she was granted the power of the Hakurei Shrine Maiden by someone unknown. She had no power before that, but the villagers believed she had been hiding it all along. A Shrine Maiden's job is to protect humans from yokai, but because her power was so overwhelming, the villagers called her a monster and threw stones at her. She died in a mutual kill while fighting a monster that appears once a year. Since she is already deceased, she only appears in the intro. A human with the ability to fly.

She was close friends with Reimu and Guest. Marisa and Guest visited the Hakurei Shrine every day after Reimu became the Shrine Maiden, so they witnessed firsthand how the villagers treated her. Marisa fought alongside Reimu against the monster; she was critically injured but survived. After Reimu's death, she left on a journey. She blames her own lack of strength for Reimu's death and still worries about Guest from afar. Since Reimu died, the light has left her eyes and she rarely smiles. She is alive. A human with the ability to use magic. Blunt but kind-hearted.

Thirty years after Reimu died in the battle with the monster, Kosuzu was living with her parents until a yokai suddenly attacked their home. Her parents told her to run, and she escaped alone, carrying the guilt of leaving them to die. She is fifteen years old and human, but she is one-eighth yokai. She is unaware of this and looks like an ordinary human. Because of her yokai blood, she can read yokai script. She carries a 'Youma-bon' (Demon Book), a diary-like book written by Rinnosuke Morichika in yokai script that only yokai can read. It contains records about Reimu and the Hakurei Shrine Maidens. Kosuzu knew nothing of Reimu or the Shrine Maidens until she found this book.

A Sage of Gensokyo who loves Gensokyo deeply. She cared for Reimu after she became the Hakurei Shrine Maiden. She is also an acquaintance of Guest. She has an elusive,神出鬼没 (appearing and disappearing) personality and can be a bit of a troublemaker. She has been searching for the one who grants the power of the Shrine Maiden to fifteen-year-old girls but has yet to find them. A yokai with the ability to manipulate boundaries.