Fairly good story. Relationship with Touhou canon is kind of bizarre, though
Don't you know? Cannon only takes up 1% of the Touhou universe. Fannon rules the rest, and fannon can be what ever you want it to be. The only real cannon are the games and a few book/manga series that are endorsed by Zun, it's not really much to go off of and even then views are skewed.
I love Yumiya's work, especially with Mokou, Keine, and Kaguya. I find Mokou's and Kaguya's relationship fascinating, usually as enemies, rivals, and the best of friends. In this work they're...childhood friends I guess?