For first time visitors to Tokyo, there are two things I'd recommend that will truly round out your Japan experience. The Sumo Tournament is one of them; even though they have been dogged by controversy these last few years, the Sumo wrestlers remain a world unto themselves, something you need to see up close in order to understand it, and the country that has created it, a little better. Taking this tour makes sense; finding things in Tokyo can be a real pain, and the Sumo stadium is not the most welcoming venue for non-Japanese speakers. You'll have a million questions about the tournament -- it's impossible to sit and watch without at least that many -- and the guides seem to either know all the answers or make them up pretty quickly.
The other thing I'd recommend: without doubt, an early morning (I mean leave your hotel at 5am) trip to the huge Tokyo Fish Market. This is most definitely NOT a tourist destination -- watch out for fast moving motorized carts hauling just-purchased tuna of enormous proportions -- you may be the only people there who is not working. But it's a sight to behold; and there are great shops within the complex selling kitchen stuff you just won't find at home; and zillions of restaurants for a Japanese style breakfast.