Eirin Yagokoro

Eirin Yagokoro is a genius of medicine from the Moon, able to create even the Hourai Elixir. She is living in exile in Gensokyo after choosing to stay with and devote herself to Kaguya Houraisan on Earth rather than take her back to the Moon. She was a very well-known figure on the Moon, having not only been instrumental in the founding of Lunar society with Lord Tsukuyomi, but also being its leading medical mind and the person in charge of the Moon's emissaries to the Earth.