Linn in Astoria is the most authentic Japanese I've had in Queens. It has an interesting vibe in that it is also an art studio with movies projected onto a wall. Beyond the artsy stuff, the food is very good --I think the chef/owner worked at Masa--and very legit. The address is 29-13 Broadway. It's an area that is now home to a small, young Japanese population, mostly college students. There is a cute little Japanese food store right next door.