sakuya is still pissed about the unfinalized player roster

Isn't Youmu the one attacking?

It's her sword slashes buch considering the scene, I'd bank on Sakuya being the invader.

I think the more horizontal swipe is Youmu breaking a few of the knives flying at her. The vertical one looks like an arcing knife to me, however by the layout of Youmu's stance it could be an upward slash that broke open the roof.

The house's gonna be a mess...

Just another day at Gensokyo.