Kaguya Houraisan is a central character in the Touhou Project, specifically making her debut in 'Imperishable Night'. She is a former princess from the Moon, now living in the Bamboo Forest of the Lost. Known for her eternal youth and beauty, Kaguya is associated with the Hourai Elixir, which grants immortality. Her character is inspired by the Japanese folklore tale 'The Tale of the Bamboo Cutter.' In the series, she plays the role of a powerful and enigmatic figure, often involved in complex plots surrounding immortality and the tension between the Earth and the Moon.