Real sushi in Hamburg?

Hey guys! I'm going to Hamburg, Germany in two weeks and since the city is a port city with lots of fish to offer I'm guessing there are some nice sushi places as well. I'm a native hamburger by birth, but haven't lived in the city (or the county...) for some 20 years. Looking for an "authentic" place mainly, something Japanese, but all recommendations are welcome. Do any of you guys have a favourite spot?