Last year, I tried 2 Japanese teas from Yuuki-cha. They were both excellent. Very aromatic and only a trace of an astringent bite. When I finally get around to ordering from ToJ, I'll include one (may two) of his black teas.
I'm glad to see this topic. I'd like to learn more about Japanese blacks. I drink one called Crimson Grove from Mellow Monk almost everyday. It's good stuff, quite sweet and I find I crave it. Easy to get in a pinch as well, delivery is almost always 1-2 days. Would love to try some other vendors though.