looking for the best sashimi.
The best I have had was at Sugiyama. See an extended post about the place on this msg board by Mao (who I went with). They get their fish from Japan (flown by courier services (daily??). The sashimi was the highlight of the meal. Beat the previous best at Nobu by a large margin, to give you a reference.
the most underrated Japanese restaurant in NY (and one of the few restaurants I know that keeps getting better and better over time) is Sakagura, nominally a sake bar in the basement of a generic office building at 211 East 43 Street (between 2nd and 3rd.
Their sashimi, like all their food, is spot-on. And fairly priced.