Why not just create two separate shops? I have a crafty friend with an etsy shop -- she made a second shop for her DIY wedding projects, but just used an extension of the same name (so, for example, if I made a second shop, I'd call it something like MietteDoesStuff so they're still related, but different. Then, include links to cross-reference them in both shops.
I imagine it doesn't make much difference, but maybe it's just a bit cleaner and more organized?
Although Rebecca, I suppose it depends a lot on whether your cards and other designs are still in that Japanese style -- if they are, I'd say keep them all together.
:)