I've been playing Catherine a lot. (I'm in the EU, we've only recently got it.) Found a save but its NA, so it won't load. Managed to get it to load, with most of the saves intact, no idea how though as I was just replacing random values, and now I need to do it again because I screwed it up.
I can't remember quite where the region data is inside a save, and all the bits you're told not to fiddle with when hex editing end and the game data begins. I've got a mostly blank file (lots of 0's), with one trophy and one save file on, and the American one with 8 save slots used. I can see the parts that I think is the data for each separate save itself and the parts that will be changed with further saving on various slots. I don't have any other EU release games to compare to either, which was my first thought.