At Osawa, the people at one table are eating classic otsumami with their sake and the couple at the next is sharing a bowl of udon; you can get both sukiyaki and foie gras with daikon; and nobody will give you side-eye if you order an albacore volcano roll or a bowl of pork chop rice - they're great! - but you can also get sushi of delicately seared nodoguro, a black-throated perch famous for its oil-free flash and robust, meaty taste, that is hard to find even in Tokyo.