I agree with Richard. The only time I've ever eaten in a restaurant that takes reservations is when a client treats me to some high-end place.

If you have never been to Tokyo, you may not realize that you can pass ten or twenty good restaurants on your way to the ones where you have reservations.

That's one of the great things about Tokyo. There are restaurants of various nationalities all over the place, as well as restaurants specializing in each subcategory of Japanese food.

When I'm in Tokyo at mealtime, I just start walking, and I never fail to find something good, sometimes something that I didn't even know I was hungry for.