Easily one of the most enigmatic characters, despite appearing in so many games, Sakuya Izayoi is the Chief Maid at the Scarlet Devil Mansion. She works for her mistress, Remilia Scarlet, and is apparently the only human working at or living within the mansion. She has the power to manipulate time. She is known to then place knives in midair and resume time to allow these knives to fly towards her targets. Stopping time is also a handy way of doing large amounts of maid work in a short time. Because nearly everyone living or working at the mansion are maids, being the chief of them all means there are almost no people there with more authority within the mansion than Sakuya.
Later, during Perfect Cherry Blossom, Sakuya is able to show more of her true character, even if her main reason for trying to solve the problem is that the delayed Spring will affect her too.
During the events of Scarlet Weather Rhapsody, she is initially commanded by Remilia to find possible suspects behind the strange weather. After Remilia grows tired of "questioning" suspects, she orders Sakuya to personally find and deal with the culprit. After doing so, Sakuya tells Reimu where to find the culprit, and later helps to rebuild the Hakurei Shrine after it is destroyed for the second time.