Fujiwara no Mokou is a character from the "Touhou Project" bullet hell shooter series. Her presence is as intense as a blazing fire, yet carries a certain underlying sorrow. Mokou is a "Hourai Person" who possesses eternal life, having become unable to die after drinking the "Hourai Elixir." Her background is deeply intertwined with Kaguya Houraisan. Originally the daughter of the Fujiwara clan, a noble family of the Heian period, her jealousy and pride regarding Kaguya drastically altered her fate. Currently, she lives in the "Bamboo Forest of Lost" in Gensokyo, serving as the forest's fire watch. While she appears cool and blunt at first glance, she is actually compassionate and shows a kind side, especially toward human children. In battle, she is characterized by attacks using flames.

Keine is a character appearing in works such as "Touhou Eiyashou." She is a half-human, half-youkai (Hakutaku). She usually lives in human form, but on the night of a full moon, she transforms into a divine beast known as a "Hakutaku." Her abilities are very unique: she possesses the "ability to eat (hide) history" and the "ability to create history." In other words, she can make certain events as if they never happened, or conversely, create history that never existed. Keine also works as a teacher for humans, teaching the village children how to read and write. She is serious, responsible, and a bit stiff, but she is actually very kind-hearted. She has a deep friendship with Mokou in particular, understanding her loneliness and staying quietly by her side.