Although satoumi is gaining attention as a form of coastal area in which various actors make use of resources and practice environmental conservation, the cooperation and relationship necessary to accomplish it have not been revealed yet. The current research investigates a satoumi community, which consists of actors involved in satoumi creation – a type of coastal management. To capture the structure, changes, and factors for changes in social networks in four developmental phases of satoumi creation initiatives, Hinase, Bizen City in Okayama Prefecture was adopted as a case study. Based on ego-centric networks of three mediators of the relationships of network actors, the structure of social network in four developmental phases was analyzed. As a result of observing the subgroups, it was found that multiple subgroups with various objectives made a multilayered network structure as the initiative developed. In addition, new subgroups were formed as entities with related objectives joined the network due to increased number of entities that act as mediators and efforts of the three main mediators. Such a finding is significant in increasing opportunities for diverse entities, including those not directly involved in the sea, to become involved in satoumi creation. As further research, the purpose of actors’ involvement in such activities, and the relationship between involvement among stakeholders and coastal management outcomes should be explored.

The existence of shrines has played an important role in strengthening ties between local communities, but many shrines were damaged during the Great East Japan Earthquake, and even today, only a few have been rebuilt. In this study, we focused on shrines located in coastal areas to understand the actual risk of tsunami damage caused by the Nankai Trough Earthquake, and organized measures for rebuilding shrines by looking at the history and challenges of rebuilding shrines after the Great East Japan Earthquake. As a result of the survey, there are 3,376 shrines located along the coasts of Japan (within 500 m from the coastline), of which 1,126 shrines are at risk of tsunami damage in the 23 prefectures that are expected to be affected by tsunamis due to the Nankai Trough earthquake. I captured what was going on. In addition, efforts to rebuild shrines in Miyagi Prefecture revealed that there were delays in shrine reconstruction due to lack of funds at each shrine and the Shrine Administration, the unregistered status of shrines, and inconsistency in application documents from each local government. The above suggests the importance of “advance preparation” in terms of systems, funds, and applications in case a shrine is affected by a tsunami.

The participatory biological monitoring survey for Osaka Bay has been conducted by a collaboration among various entities since 2008. We analyzed distribution of 34 representative macrobenthos and its factor of changes in the distribution area with water quality. The percentage of occurrence of two macrobenthos species increased and that of 5 species decreased over a 12-year period. The results of water quality monitoring in the coastal area of Osaka Bay showed that TN and TP decreased overall and water quality changed, while nutrient levels remained high in the inner part of the bay. Factors contributing to the distribution of barnacles and representative attached bivalves were analyzed using logistic regression analysis, and were considered to be related to trophic state such as TN. Data from a long-term citizen survey reaffirmed the usefulness and role of citizen participatory biological monitoring in the coastal areas of Osaka Bay.

In recent years, the frequent disruptions of international straits, canals, and ports have drawn serious attention to the significant risks they pose to global trade and economy. A navigational disruption of the Tokyo Bay Central Fairway, a critical access route to all ports in the Tokyo Bay, could have a profound impact on the economy and society in the Tokyo metropolitan area. This study developed risk scenarios for navigational disruption of the Tokyo Bay Central Fairway by analyzing various disaster events and the transmission mechanism of such disasters. As a result, the possibility of navigation disruption due to ship accidents, cyber-attacks, and volcanic eruptions cannot be ruled out. In the worst case, navigation may be suspended for about a month and restricted for a year or more.

As an international norm for sustainable development, Stakeholder Engagement (SE)—a process in which stakeholders affected by a project’s implementation participate in decision-making and build consensus—is increasingly emphasized. This paper examines SE in the context of the floating offshore wind power demonstration project off the coast of Fukushima, using the five features of the SE framework proposed by Talley et al. (2016). The study identifies key challenges related to SE in marine development in Japan, including the concept of "coexistence with fisheries" and three stakeholder-related issues: the identification of fishers participating in decision-making, pressures from an expanded group of stakeholders, and the impact of interactions among stakeholders on SE. SE is itself a project, and conducting a "reflection on processes and outcomes" at the end is a crucial step in pursuing more effective SE practices.