Born outside of Gensokyo under circumstances rarely disclosed, Sakuya Izayoi was a vampire hunter and exterminator, before she eventually became the head maid of the Scarlet Devil Mansion under its vampire mistress, Remilia Scarlet. Renowned for her ability to manipulate time and near-perfect professionalism along with other supernatural abilities, she is responsible for managing nearly every aspect of life within the mansion.

Her life changed in 2005 when Blake Izayoi was spirited into Gensokyo following the Phantasmagoria of Flower View incident. During the months-long incident caused by his arrival, the two grew close.

Following Blake's decision to sign a blood contract with Remilia Scarlet and permanently reside at the Scarlet Devil Mansion, their relationship continued to deepen, and the two eventually married on November 18th, 2006. Since then, Sakuya has remained both Blake's wife and closest confidant.

However, her life, too, would change alongside her husband's, when a mysterious yakuza-like man by the name of Kazuki Murasaki was found right at their doorstep, buried under snow and dying... The rest is history.