Tsukiji Fish Market is the source of much of the seafood in the Tokyo area, and the morning hours are the busiest. At 3:00 AM, the fish is laid out and inspected to prepare for the tuna auction. This auction lasts from 5:30 AM to about 9:00 AM.
Starting at around 8:00 AM, the middlemen start distributing their newly bought tuna to their stores all around Tokyo. As the day gets hotter, it gets harder to keep the fish fresh, therefore the market closes at about 1:00 PM and clean up begins.
There are many wonderful sushi restaurants in and around the market, which buy only the freshest fish for their dishes. This is a great place to go if you want to experience amazing sushi. But please be prepared for the fishy smell.