There are Japanese/sushi places dispersed throughout the island, but a lesser known one is Yume. It is located on Park Street, with its entrance hidden between a nail saloon and a gift shop. A narrow staircase leads you upstairs to the restaurant, which is a nice cozy little place. There are 4 quaint tables along the wall, with a great view of the people and traffic below you on Park Street. You can also sit at the bar.
My friends and I have ate there twice. The first time sitting at the bar, and the second at a table. I preferred the bar. The fish is fresh, and from the bar, you can watch as the chef makes your order. They had a nice selection of sake, as well as sushi. Everything is made fresh and in front of you. It is a worthwhile experience in itself just watching the chef. He works quickly, and the sushi in addition to being delicious is also beautifully displayed.