Eirin Yagokoro is a brilliant and mysterious doctor from the Touhou Project series. Known as the 'Brain of the Moon,' she possesses vast knowledge and wisdom, having originally come from the Lunar Capital. Eirin serves as the primary doctor of Eientei, a hidden mansion in the Bamboo Forest of the Lost. She is deeply loyal to Kaguya Houraisan, aiding her in escaping the Moon. Her role often involves crafting potions and medicines, and she is known for her calm demeanor and exceptional intellect. Her presence adds depth to the series' lore, blending mythical and scientific elements.