When you visit Japan, you would be regret going home without eating sushi.
Sushi is the food which represents Japan. A lot of sushi restaurant are in Japan. Especially, a market which is called “Tsukiji” near there. People buy and sell fresh fish, vegetables and so on. (http://www.tsukiji-market.or.jp/) So, you could eat sushi with fresh fish in Tokyo.
By the way, do you know “rotation sushi”? As the name shows,
sushi are placed on a rotating conveyor belt or moat that winds through the restaurant and moves past every table and counter seat.
(In Wikipedia: The Free Encyclopedia. Retrieved from http://en.wikipedia.org/wiki/Conveyor_belt_sushi)
One plate is almost 100yen and payment depends on how many plate you took from the belt. You could make your stomach full with reasonable price.