Well, this was one hell of a ride! This one right here really just encapsulates a great character growth story. From the way that their story started to the various points that have shaped Yukari to the person that she would be in the finale, everything is seriously on point with this series.
Honestly an epilogue chapter that helps to tie to the current Yukari and Ran that is known in the Touhou Franchise would be all there is left for the author to make this the official headcanon of the Franchise itself. (Well it indeed already is my official headcanon already.)