Concerning the dangers of sushi: I have a very delicate tolerance threshold regarding fish and sea food, so I sent back the surimi (fake crab meat) sushi.

The rest was fine, we had tons of sake-sushi that tasted neither frozen nor off.

Edit: I just noticed that there are two Natsu restaurants, Gumpendorfer Straße 45 is the one where I ate. they share menus and advertising, so I presume they are very similar.