The Sakura in Agana, if it's still there. Best tempura I ever had. Couple of REAL sushi bars on the island too, as I recall. The kind where you point at what critter you want and the obsessively-compulsively clean chef wipes the whole kitchen spotless before he cleavers the hell out of your selection and then serves it to you with a smile. There were a couple of Japanese restaurants, too, with the little stoves in the center of the table...where you cook your own foods. Look for the places were you have to sit on the floor. Warm sake is a treat too, if you drink. It sneaks up on you though. We watched a group of reserved Japanese businessmen in the Sakura once enter and take their places on their cushions around their long table, and as they ate they started knocking back little cups of sake. An hour later they were falling off their cushions and laughing at each other. Try wasabi mustard and pickled ginger root...standard Japanese condiments. Wasabi is the hottest thing I've ever tasted, but it has no oil base like jalapenos and such, so it doesn't stick to your tongue. Just gives you a feeling like an ice cream headache squared, and just as the pain is about to make you scream...it's gone. Great for the sinuses. And pickled ginger root may be the best tasting stuff on earth. Oh, and pick up a bag of dried cuttlefish sometime. Like beef jerky. makes a great snack. Look for the markets, too, where you can buy whole dried cuttlefish, then look around that market for some of the strangest foods you'll ever come across in your life.