Reddit mentions of Mitoku Organic Mikawa Mirin - 10 oz.

I cook Japanese regularly. The nice thing about Japanese in your case is that there aren't many staples and they're all quite shelf-stable. Once you have them you can make a ton of dishes (unlike, say, Chinese which has a million different ingredients). But a couple of them could be hard to source. Sake and mirin have come up already and those are the hardest to get in decent quality. The mirin at supermarkets is aji-mirin, which is heavily spiked with high fructose corn syrup. The real stuff has alcohol in it, so it's bound by liquor regulations. Mitoku mirin is excellent but it's expensive to begin with and even more so on Amazon. 3 packs of Eden are more reasonable but that's a lot to buy. Takara is decent too but Amazon doesn't stock it. Sake is also a pain. You might find Gekkeikan or another cheap sake at a liquor store. Probably not, though. And that's really nasty sake. OK for cooking but I wouldn't drink it. The best cheap sake - by far - is Sho Chiku Bai, which is cheap because it's made in California and not Japan. It's only $6/bottle by me and it's even drinkable. If you get into cooking Japanese you might see if you can source a case of it.

If you can find those two items (or settle for crappy versions to get started), order up some kombu, katsuobushi, and miso paste online to go with them. From there, you can cook 90% of Japanese recipes with some occasional subs for produce. Tick the "most popular" filter on the recipes at JustOneCookbook to get a great list. Some favorites around here include gyudon, oyakodon, tempura, and miso salmon. And miso soup too, of course.