This is my favorite of the secret projects so far. It's clearly heavily inspired by Your Name but still feels original. Yumi and Painter felt equally developed and each had excellent and intertwined character arcs. 
I'm writing this spoiler free so I'm being vague in this but I felt that the narrator in this story wasn't quite as heavy handed as in Tress and their intersections were just enough.
The only thing I didn't love is I didn't fully buy the friends motivations in not believing Painter. I get that it was a hurtful thing but I feel it would have made more sense had his backstory included more similar mess ups on his part. 
This is easily one of my favorite stories in the cosmere and I feel you can read this without having read other cosmere books. It does reference Stormlight quite a bit but not in a way I feel spoils that story.