Let me preface this post by saying that San Francisco is by far the most amazing city I've ever lived in for quality of amazing, interesting restaurants.
However, having lived in San Diego for almost five years, I feel as thought San Francisco is sometimes lacking in the sushi department. Don't get me wrong, there are fantastic sushi restaurants in the city. But in San Diego, they are everywhere. In San Francisco, you have to look a little harder. A field trip to Koo in the inner sunset is one of those hidden gems.