The restaurant is specialized in Shabu (a japanese style Fondue-like dish with thin sliced beef which is cooked in boiling water). The food is quite good but not really cheap. You can choose from different kinds of beef ranging from imported beef up to super-premium japanese beef. The place has a nice (kind of traditional) atmosphere and very friendly staff.
Be careful: Shabuzen is in the basement of the building. There is also another (quite expensive) restaurant in the ground floor of the same building.