The use of Renewable Energy (RE) is becoming popular for its clean and safe characteristics. The development of RE is also one of the crucial steps for the future sustainable development of energy resources. Nowadays, rural areas are facing issues such as depopulation and economic decline. How to find solutions to these issues while aiming to achieve sustainable development is a challenging task. Rural areas with RE in Japan and China have been established recently, and there are a few practical cases worth referencing. To identify key factors for RE promotion and its sustainability values in rural areas, this study presents two pioneer cases: Kuzumakicho in Japan and Chongming Island in China. Each of them stands for strong RE advancement in their home country and bears specific characteristics. Instead of a comparative study, this study examines the two cases as parallel case studies using a review of the literature, local plans, policy documents, and a questionnaire sheet with a SWOT analysis approach integrated in the methods. Key factors included municipal planning concepts and subsidies from national or regional governments among others, while contributions to sustainability include environmental education, local tourism, disaster prevention/mitigation, and waste re-use among others. In conclusion, the lessons learned and recommendations for future RE promotion in Japanese and Chinese rural areas are given.