I've been visiting Kumai regularly for the past 3 years. It's consistently good food, the staff are very friendly and there's always something new to try.
I think the best description of Kumai is Japanese comfort food. The sushi is excellent, but the real treats are their cooked dishes: bento, Japanese curry, noodles, chawanmushi, and so on. I'm also a huge fan of their maguro yamakake.
My only complaint is their menus aren't accurate. I recommend asking the server for recommendations. Ask for which sushi she recommends, or what seasonal dishes they are offering. They often have interesting items not listed on the menu. Definitely worth a visit.