I had a dream last night about Sakuya. I know exactly why I was dreaming about it: I read a doujinshi about her. It is called "Touhou - The Maid and the Bloody Watch of Fate". There are two chapters, plus one R18 chapter on a separate page. While there is a lot of explicit stuff, it is still a great continuation of the story, fan-service aside. But be aware, about half of the chapter is 18+ content.
The first two chapters are on the first link. The premise of the doujinshi is, in spoiler-free terms, about Remilia acting selfish, as usual. Minor spoiler of the plot:
Remilia tries to turn Sakuya into a vampire, but I won't say if she succeeded or not.I literally cannot stop thinking about it to the point where it literally invaded my dreams, as stated earlier. It's not only because it's really good, but because of the significance of the overall message that it tries to explain to the fandom about Sakuya's personal values.
It is available to read on MangaDex. While the R18 one is pretty heavy on fan-service, it adds on to the story quite a bit and is still worth checking out.
Touhou - The Maid and the Bloody Watch of Fate:
https://mangadex.org/title/39bd0417-5b2b-4d0e-b227-bcefe0987df9%E2%80%A6R18 Warning: Touhou - The Maid and the Bloody Watch of Fate Lunatic:
https://mangadex.org/title/a6e352e5-dea2-4a3a-8f9f-58f0d1c51824/touhou-the-maid-and-the-bloody-watch-of-fate-lunatic [ Attachment: You are not allowed to view attachments ]