Sakuya Izayoi is an antagonist who made her debut in the sixth installment of the Touhou Project series, the Embodiment of Scarlet Devil. She is skilled at throwing knives, and also has the ability to manipulate time, and to an extent, space. She's also known as an incident resolver, and is deathly loyal to her mistress, Remilia Scarlet.
- (Touhou 9) Dark blue eyes, silver hair, has a long braid on each side of her face with green bows at the ends, she carries many knives. Wears a pink and dark blue French maid's outfit with long sleeves, and a white maid headband on her head. The Roman numerals for 1 through 12 line the bottom of her apron.
- (Touhou 9, alternative outfit) Same as above, but her outfit is mainly dark red instead of dark blue.
- (Touhou 7.5, 8, 10.5) Same as Touhou 9 outfit, except her apron has no text and is wearing short sleeves.
- (Touhou 7.5 and 10.5, alternative outfit) Same as above, but her outfit is mainly light blue with a white apron and her hair is light green.
- (Touhou 7) Same as Touhou 9 outfit, except her apron has no text and is wearing blue colored long sleeves and a red scarf.
- (Touhou 6) Same as Touhou 9 outfit, except she had bright red eyes, short sleeves, and the phrase "Red Magic" embroidered on her left sleeve.
- Remilia Scarlet (Mistress)
- Patchouli Knowledge (Mistress's friend)
- Flandre Scarlet (Mistress's younger sister)
- Hong Meiling (Fellow employee, Friend?)
- Eirin Yagokoro (Unknown)
- Koakuma (Unknown)
- She is a character from the spin-off series Koumajou Densetsu and is the main protagonist of Koumajou Densetsu II: Stranger's Requiem.
- Sakuya claims she's in her late-teens, but Hieda no Akyu says Sakuya's refined manner and the level of her ability seems like that of a human that's been living for hundreds of years. According to a quote from Remilia Scarlet and Sakuya's ending in Imperishable Night (Good Ending #3), Sakuya has been working at the Scarlet Devil Mansion for so long, Remilia doesn't feel it fitting to call her human. With a comment like that, it seems safe enough to assume she has been at the Scarlet Devil Mansion for an extremely long time.
- Hieda no Akyuu believes Sakuya has managed to live so long while still looking like a teenager by manipulating time. It's true that Sakuya can increase the speed at which something ages, such as making bamboo flowers bloom instantly in Marisa's A ending of Embodiment of Scarlet Devil, even though this would normally take sixty years. It seems safe enough to assume she can decelerate aging for a specific object, too.
- Despite helping rebuild the Hakurei Shrine later in Scarlet Weather Rhapsody, Sakuya casually ignores Reimu Hakurei's donation requests for shrine upkeep in Immaterial and Missing Power, saying she doesn't believe in gods anyway.
- Sakuya's involvement in the human cuisine of the Scarlet Devil Mansion is unknown. The Scarlet Devil Mansion has humans to eat, but Sakuya has never been shown preparing humans to eat. She has been shown to seek out rare (non-human) ingredients as well as prepare noodles and tea (accompanying context/dialogue usually implies it's not human), but the closest she has ever been depicted cooking humans was asking Remilia if she thought her latest (not humans) tea tasted like blood in Strange and Bright Nature Deity. Eiki Shiki, Yamaxanadu lectures that Sakuya's sin is coldness towards humans, with nothing about cooking them. Flandre Scarlet confesses to Marisa Kirisame in Embodiment of Scarlet Devil that she has no idea who prepares her human food, but doesn't think it's Remilia. Music comments in Embodiment of Scarlet Devil by ZUN state that Remilia's tea is blood, but the tea Sakuya serves in most official works is usually implied to be normal tea with Sakuya's latest experimental ingredient. Sakuya's ending in Immaterial and Missing Power mentions that tea time is usually "red tea", which is perhaps separate from the experimental teas Sakuya personally prepares. Could the usual non-experimental "red" tea be blood, and does Sakuya realize this?
- Sakuya is constantly seeking out new varieties of tea flavors for Remilia to try, as shown in several official works. For example, she mentions in Phantasmagoria of Flower View that with so many flowers around, she can make as much tea and as many pastries as she wants. (Flowers have often been used to provide flavoring for tea, especially in the past, and are still the basis of jasmine tea.)
- In the games, it is shown Sakuya has the ability to make knives appear mysteriously when time is stopped, but in her artwork in The Grimoire of Marisa, she is shown placing the knives physically.
- Her alternate outfit in Immaterial and Missing Power and Scarlet Weather Rhapsody is a homage to Ruukoto, the first maid of the Touhou Project. In Touhou Hisoutensoku more alternate outfits were added, including a Shinku palette and a Dio Brando palette.
- She Has Everlasting Hatred towards All Subjects Possessing Any Danger to Scarlets.