Although Japan is one of the largest seafood-consuming countries, with various types of seafood products traded throughout the nation, few studies have explored how this market is integrated from the aspect of market price. Because Japanese consumers in different regions have different preferences for seafood, we focused our study to see how the regional seafood retail markets (Tokyo, Osaka, Nagoya, Sapporo, and Fukuoka) are integrated for 10 major seafood products (horse mackerel, short-necked clams, yellowtail, scallops, cuttlefish/squid, flounder, tuna, mackerel, saury, and octopus) consumed in Japan. We applied the relatively new Phillips–Sul convergence test for our analysis. For most of the seafood products investigated in this study, our results indicate that the Japanese regional seafood markets cannot be integrated as a whole and that marketing strategies need to consider the peculiar characteristics of the regional seafood markets.