Sushi resturaunts always have other options on the menu. Although its a much smaller selection, they usually offer lunch/dinner plates with chicken or beef.
Again, there is also sashimi and miso soups, as well tempura.
If you want to go low carb, I suggest an order of shrimp tempura and veggies with a bowl of miso soup. It can fill you right up and be your meal for the night.