Located only blocks from Tokyo's glittering Ginza, Tsukiji—the world's largest marketplace for seafood—is a prominent landmark, well known but little understood by most Tokyoites: a supplier for countless fishmongers and sushi chefs, and a popular and fascinating destination for foreign tourists. Early every morning, the worlds of hi-tech and pre-tech trade noisily converge as tens of thousands of tons of seafood from every ocean of the world quickly change hands in Tsukiji's...