Kiku is nice because it is rather quiet and one can ask for special needs diet stuff without feeling like a burden. They are really nice about not using butter or fish sauce (their teriyaki sauce has animal product in it). When you get there, just say you are vegetarian and would like oil to be used on the vegetables instead of butter. Ask for only soy sauce and ginger sauce. Their miso soup is vegan, but I am not sure about the hibachi soup. I usually get the hibachi soup traded for miso when I get the vegetable delight hibachi. The salad that comes with it is also vegan. Also, ask for no shrimp appetizer.
Other items at Kiku are a variety of vegetable sushi including inari, avocado, and asparagus. They also have edamame and seaweed salad.
For a complete review, please see my blog here: http://veganmiss.blogspot.com/2011/08/vegan-springfield-il-part-two.html