In Japan, fisheries’ product has decreased since the 1980s, and the government amended the fisheries law in 2020 to shift to managed fisheries. However, awareness of seafood sustainability is still low. This study identifies the reason for the low awareness and states the necessary actions to increase sustainable seafood consumption. The proactive stakeholders in seafood supply were surveyed to determine the current status of sustainable seafood sales. Marine Stewardship Council-certified fishers and MSC’s Chain-of-Custody certification holders answered the questionnaires. Fishers showed a positive attitude, citing proactive sales channel expansions and contributions to sustainability. Distributors were primarily passive, mainly because they obtained the certification at the request of their clients, and about half of them did not disseminate information between consumers and suppliers. Both fishers and distributors expect the government to promote campaigns and education. The stages of the awareness of producers, intermediary trade, and retailers are different and did not align. Therefore, if the supply chain stakeholders proactively educate themselves, choose sustainable products from the fishers, and pass the sustainability information to the consumers, sustainable seafood consumption would progress.