[Purpose/Significance] This paper focuses on the development process and service mechanisms of Japan's Research Data Cloud (RDC) system, a core national infrastructure coordinated by the Research Center for Open Science and Data Platform (RCOS). Against the backdrop of growing global attention to open science, RDC presents a practical model for integrating data management, open sharing, publication, search, and preservation throughout the research lifecycle. The paper highlights the unique collaborative model of RDC, which is characterized by a small team driving large networks. Compared to prior literature that often emphasizes technical architectures or isolated institutional efforts, the paper situates RDC within Japan's broader open science strategy, offering both theoretical and practical insights. It explores how RDC contributes to advancing the FAIR data principles, supporting cross-sector innovation, and strengthening national science and technology governance. The analysis also offers strategic lessons for China in building a sustainable and service-oriented research data system. [Method/Process] Using a qualitative case study approach, the paper draws on a combination of primary and secondary sources, including official reports, project documentation, and academic literature, and publicly available platform data related to the RDC initiative. It systematically analyzes the organizational structure and collaborative mechanisms of RDC, focusing on the institutional roles, platform components (GakuNin RDM, WEKO3, CiNii Research), and key technological innovations such as data governance, data provenance, secure computing, and trusted storage. In particular, it analyzes how RCOS functions as a neutral coordinator that bridges stakeholders across ministries, universities, and research organizations, and how it plays a role in translating policy mandates into technical services, integrating institutional workflows, and fostering community participation in the open science ecosystem. [Results/Conclusions] Despite constrained resources, RDC has developed a comprehensive research data ecosystem that serves researchers, data managers, librarians, industry, and the public. Japan's experience demonstrates that emphasizing interoperability, governance coordination, and capacity building, especially through small-scale research teams and nationwide collaborative networks, can effectively support the development of robust research infrastructure. The paper concludes by proposing several recommendations for China: the creation of independent coordination agencies to avoid fragmented development, the establishment of standardized service frameworks to enhance interoperability, and the implementation of tiered training programs to improve data literacy and management capacity across disciplines. Future research should further explore comparative institutional models, examine the long-term sustainability of open science ecosystems under different governance conditions, and investigate the cultural, legal, and technical dimensions that shape localized approaches to research data governance.