Sakuya Izayoi

Sakuya Izayoi is the Chief Maid who serves Remilia Scarlet, the head of the Scarlet Devil Mansion. She is the only human living in the Scarlet Devil Mansion. Sakuya tends to be a little spacey, but it's unknown if its just an act. She's polite and pleasant towards to her mistress Remilia Scarlet and those she's close with, such as Patchouli Knowledge, while being less formal with other people. With those she's frequently annoyed with, such as Marisa Kirisame, she can be somewhat harsh and direct with her insults and smack-talk, especially during duels. Sakuya seems to lack knowledge of basic scientific concepts, such as "humans need oxygen to breathe," as seen in both Silent Sinner in Blue and her route in Unconnected Marketeers. Ironically, she has also stated that she is an "atheist" on multiple occasions, such as in Wild and Horned Hermit, despite living in a land where Gods are literally real. As for her age, ZUN directly stated that "she plays the role of a human maid about 10 to 20 years old" and "perhaps she is a character in her early teens, and in Perfect Memento in Strict Sense, according to Hieda no Akyuu, "she claims to be in her late teens", but acts with the mannerisms of someone and the level of her ability seems like that of a human that's been living for more than a hundred 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.