Review: Actually, I noticed the macrobiotic set dessert seems to contain honey so technically there is no set that is completely vegan, and no truly vegan dessert option. It seems that 3 out of 4 curries and both salad dressings in the curry buffet are vegan though. The bread probably has butter or ghee on it unless you request it otherwise (they always ask when I order the macrobiotic set). I am not a huge fan of curry, but I find Nataraj's to be very delicious. Also spicy, but not overwhelmingly so.
They have stopped having the buffet at lunch, but now I can get a curry set AND soymilk tapioca for about the same price. It's about what I would get at the buffet but with more rice and less curry. As of right now, curry sets A, B, C, D, and G are vegan if you choose rice (and not nan bread). The lunch menu still isn't helpfully marked like the dinner menu, but if you can read Japanese the milk-containing curries say "milk" or "creamy" in the description.
The vegan-friendliness of the buffet varies widely. It could be all vegan curries (meaning everything but the nan bread is vegan) or only half vegan curries and not well-labeled, depending on the day. (The dinner menu is clearly labeled but also costs a lot more, and the sets aren't very vegan-friendly. The amount of food I get for 1000 yen at lunch costs me 2500 yen or so at dinner.)