The left shadow appears to be Nagasaki Soyo, based on the loose hair strand. Based on the bangs and the expressions the right shadow appears to be Chihaya Anon.
We don't know for sure that this is Cannock's sister
If it’s not her, then everything simply gets retagged. (Only example I’ve personally seen) Like how everything Project Mugen was retagged into Ananta once the title was revealed.
It's referring to a recent trend of turning photos, pictures, screenshots, etc. with AI into Ghibli-styled pictures like the one here, except this one is hand-drawn, hence the tag.