I might have made an Yveltal list for you in the past? Could have another Yveltal collector on reddit, though.
Some good news however: this thread I created as overview of all languages sets are released in is mostly up-to-date, and I see the unlimited edition Japanese Red Flash nor Cruel Traitor most likely weren’t printed (not 100% sure, but I’m 99.5% sure they weren’t), so it seems your Japanese portion of your collection is already complete. 
EDIT: Apparently I was mistaken, and the Cruel Traitor set does exist in unlimited edition after all. Still not sure about the Red Flash set.
As for some cards that have an Yveltal cameo (although you might have already been aware of them):
Steam Siege 116/114 Gardevoir EX
Victory Ring 1st place XY-P promoBest of luck with your collection goals!
Greetz,
Quuador