In recent years, urban river spaces have been increasingly utilized by incorporating private-sector initiatives, driven by a renewed recognition of their environmental value and rising demand for their use as public spaces. This study examines the areas surrounding the Kitajikken and Shiodome Rivers along the Sumida River in Tokyo, focusing on private-sector efforts utilizing the river occupancy permit system and the nature of the public-private partnerships that support them. In both case studies, a clear division of roles between public and private sectors was observed, alongside the development of area-wide urban design that extended beyond the officially designated occupancy zones. In addition, sustained collaboration with local residents through established consultation bodies contributed to maintaining the public interest in operations. However, challenges remain, including the high entry barriers posed by the need for strong public benefit and trustworthiness in order to obtain occupancy permits, as well as issues related to the implementation of the institutional framework.