An interesting take on a touhou dialogue routes.
I honestly felt like playing the game with a Letty mod, its very interesting to see this kind of art style, the only thing that I found weird were that some characters had larger necks xD. even so, I loved all of them even if for some reason, yuyu has a darker shadow on her face that doesn't fit with the rest.
Also, weren't most of the backgrounds supposed to be set on winter?
Still, great story, I think the ship is kinda hard to achieve, since sakuya did all this for her mistress and as the bad endind implied, she immediately returned to remi's mansion, but hey, this was just a theory, a fanfic theory, thanks for writing.