Quick translation (not mine) from ZUN's blog
I've made the perfect game for summers like this!
It's what I'll be releasing next Comiket.
Touhou Project 12.8 (how far are we cutting these?)
It is: "Great Fairy War ~ Touhou March Spirits
Basically, Cirno has declared war on the three fairies. This is a continuation of the books of the same name.
Actually, I was planning to make a game like this since before the release of Strange and Bright Nature Deity book two (the text in that book titled "Great Fairy War" was the opening story for that), but my schedule and other stuff got in the way, and I wasn't able to make it a reality until now! (Just kidding, I'm still diligently working to make it a reality)
Hirasaka Makoto drew the pictures for me, and was able to change it the unusually airy world of Strange and Bright Nature Deity (ah, I got permission from Kadokawa, of course).
Anyway, the game's subject matter is something like this:
"A refreshing game where Cirno advances by freezing danmaku that she ought to be able to dodge."
It's turned into a game where one can sit down and play without thinking, with the difficulty so that it can be replayed again, with bold yet detailed patterns.
(Note: it is under development, and its appearance may change.)
It's a simple game where you don't really need to know about the story or characters and can just play, so for those who like games, please try it.
Of course, the version I release at Comiket will be completed!
Oh, my booth number is East A-28a on the second day.
Though, I haven't finished it yet.