Eirin Yagokoro (八意 永琳 Yagokoro Eirin?)
Species: Human (Lunarian)
Ability: Creation of any medicine, natural genius
Theme Song: Gensokyo Millenium ~ History of the Moon
Boss of Final Stage A and midboss of Final Stage B. A genius pharmacist who once lived on the moon. Kaguya persuaded her to produce the forbidden Hourai Elixir—the elixir of life—and consumed it. They were found out, and Kaguya alone was punished and was sent to the Earth, a fact which Eirin always felt guilty about. Some time later, the moon court pardoned Kaguya's sins and summoned her back. Eirin and a handful of emissaries were sent to retrieve her, but Eirin found out that Kaguya didn't want to return to the moon. Acting out of her past guilt, Eirin betrayed and murdered all the other emissaries under the eyes of the earthlings who had fostered Kaguya. Eirin bribed the earthlings with the Hourai Elixir, in order to keep them silent, and went into hiding with Kaguya in Gensokyo. She is based on the Japanese goddess Omoikane.