Using a case of the Sekisei Lagoon, Okinawa Prefecture, the southeastern tip of Japanese archipelago, this chapter discussed the interrelationships among the sectoral policy interventions by various marine-related ministries, and the whole structure of the integrated ocean policy. First, we developed the Social-Ecological Systems (SES) Schematic, which summarized the main ecosystem structures, functions, use types, and the stakeholders relating to the Sekisei Lagoon. Then, sectoral policy interventions by various ministries were overlaid onto the SES schematic to graphically show their interrelationships. We found that the ecosystem structure and functions used by one sector is closely connected to other structures and functions, which are then used by other sectors. In other words, all the stakeholders in the social system are closely interlinked at the ecological system level. Secondly, all in all, sectoral policy interventions by various ministries are covering almost all part of the Sekisei Lagoon SES, and therefore, the total coordination of the sectoral policy interventions and the creation of the synergy effects are required. In this process, the cabinet office and the local government will play the important roles. Finally, this SES schematic can be used as a boundary object to facilitate the knowledge exchanges among various stakeholders including the policy makers, practitioners, and researchers, to share the common understandings of the current situation, and to cocreate the policy interventions for the sustainable uses of Sekisei Lagoon.