An immortal human with powers of pyromancy. Mokou bears a deep grudge against Houraisan Kaguya for spurning her father's hand in marriage when the former was still young (in the process humiliating him), stealing and drinking the Hourai Elixir in revenge. Upon reaching Gensoukyou, she learned that Kaguya, too, was an immortal exile, and both have since engaged in countless, often fatal, duels, only for the vanquished to be resurrected each time. When not picking a fight with Kaguya, she rescues lost people or guides them through the Bamboo Forest to Eientei, home of her own nemesis, or the Human Village, where her friend Kamishirasawa Keine lives, and claims to run a yakitori stand (which would put her at odds with Mystia Lorelei).
Becomes playable in Urban Legend in Limbo.