As both material entities and “packages” of genetic information, seeds are a common—a co-managed natural resource—in communities and regions all over the world. In this analysis of Japan’s national potential for a commons approach to seed sovereignty, Norie Tamura looks through the lens of institutional change. In 2017, the revocation of the Main Crop Seeds Act, a law upholding the state-run seed system, triggered a major backlash in Japanese civil society. Many in the movement called for a revival of state control without fully recognizing the part it plays, for instance, in agricultural industrialization. Yet simultaneously, a range of seed commons exist in Japan at the village and prefectural level, as well as through the network maintained by the Japan Organic Agriculture Organization. For seed commoning to spread and consolidate in Japan, Tamura asserts a need for reintegrating the producer–user divide and fostering open communication between seed and civil sectors.