What should I bring back from Japan?

I'm off to Japan in a couple of weeks, so now that all the arrangements are made I've started to wonder what I'll be able to bring back. (I know it won't be as much as I want!) I probably can't go for anything heavy, bulky or perishable, and I'm going to try really hard to avoid going crazy on bento accessories, because I already have enough that I don't use regularly enough. So I was wondering if anybody had any recommendations of things that you can only get in Japan that would make a difference to cooking Japanese-style. The only thing I've thought of so far is a drop lid! I'm never convinced that the recommendation to make parchment/foil ones work as well. Oh, and I'll probably get some pickled plums. I love them, but the only place I know does them in the UK is the Japan Centre, which isn't exactly close to where I live... Can I ask another question too? I've read that it's not very common for credit cards issued outside of Japan to be accepted in shops. I'm quite happy to carry cash, but I think I might have a spending binge or two it would be nice to just stick it all on the card without having to total up my purchases and check my purse! Is it likely that large stores (I'm thinking my main destinations are going to be department stores, Loft, Kinokuniya) will be happy with a UK Visa card? If anyone's interested, our itinterary takes in Toyko, Hakone, Matsumoto, Kyoto, and Takayama. So any recommendations linked to those places would also be welcome!