Flandre Scarlet might appear as an adorable little girl, but she is actually a vampire almost half a millennium old. She is the younger sister of Remilia Scarlet a.k.a. The Scarlet Devil, earning her the name Sister of the Devil. She lives in the Scarlet Devil Mansion—which she hardly ever leaves—with her older sister, Sakuya Izayoi, Hong Meiling, Patchouli Knowledge, the Fairy Maids, the hobgoblins, and Koakuma. Due to this isolated life, she has never seen a live human before her encounter with Reimu Hakurei or Marisa Kirisame.
She first appeared in Embodiment of the Scarlet Devil, which is the sixth game in the Touhou Project games by Team Shanghai Alice (ZUN), and the first written for Windows. Players can also encounter her in Shoot the Bullet, the book Bohemian Archive in Japanese Red, the comic Inaba of the Moon and Inaba of the Earth, and the official Touhou comic Forbidden Scrollery.