THIS JAPANESE SAUCE IS ONE OF THE BEST THINGS I HAVE EVER TASTED.

This sauce is utterly beyond description in terms of its goodness.
One commenter pointed out that I didn't mention where to find this. I purchased it at World Market, which has locations all over the Puget Sound, but the easiest way to get it is probably to order it from their website. They are selling it on there, but who knows for how long!