I had dinner at 69 Leonard last week and the nigiri course was simply amazing. Chef is producing rice for the course, which at the moment is probably the best I ever had in NYC. Add to that a fastidious dedication to only the best fish and you have a simply perfect end product.
So, technically IMO a Kaiseki restaurant in NYC is serving some of the best nigiri in NYC.
How can this be? Chef Derek (besides his Kaiseki training at Kikunoi) apprenticed at Sushi Aoki in Tokyo for five years. He was such a good student that his teacher Chef Aoki set him up with a pop up in GInza. Derek knows what he is doing with sushi.