I love sushi and I particularly like it when food is served in a creative way. The castle is a really nice way for the restaurant to do the difficult job of serving a dish in an interesting way even though there are many people ordering many different kinds of food.
If you click on this picture of prawn sushi there are several other very fun sushi shapes - this is my favorite though.
I'd like to be able to make this kind of sushi but I will admit. It is art and I can appreciate other artists but I'm too lazy to practice doing art that someone is going to look at for 5 minutes then eat.