An immortal human with powers of pyromancy. Has long white or very pale blue hair, red eyes, and wears suspenders with pants. Mokou bears a deep grudge against Kaguya for spurning her father's hand in marriage when the former was still young (humiliating him in the process), which caused her to steal and drink the Hourai Elixir as 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).
Became playable in Urban Legend in Limbo.