Through the Clinical Innovation Network, Japan’s regulatory authorities have enhanced the development of registries that utilize real-world data (RWD). The Ministry of Health, Labour and Welfare has issued guidelines, whereas the Pharmaceuticals and Medical Devices Agency has conducted consultations to manage and verify the integrity of these registries, thus improving the framework for the effective use of RWD. The use of cancer registry data as an external control group has been promoted by regulatory bodies and academic institutions. Given the aforementioned background, several high-quality cancer registries, such as the ‘SCRUM-Japan Registry’, ‘MASTER KEY project’, and ‘GALAXY registry’, have been established. The SCRUM-Japan Registry has been instrumental in achieving the world’s first regulatory approval for human epidermal growth factor receptor 2 (HER2)-positive colorectal cancer, demonstrating the value of regulatory-grade registries in managing rare molecular subtypes. However, the broader adoption of registry data for regulatory use in Japan remains limited, primarily owing to the lack of clear standards for using RWD/real-world evidence (RWE) for drug approval. This uncertainty has made pharmaceutical companies hesitant to use such data for regulatory submissions. This review aimed to elucidate the perspectives and related guidelines of the regulatory authorities concerning cancer registries in Japan. In response, the ‘REALISE study’ was initiated to define the ‘relevancy’ and ‘reliability’ of data necessary for new drug approvals and to develop methodologies to ensure data reliability retrospectively. The findings of this study will inform the creation of draft guidelines aimed at broadening the application of RWD/RWE throughout Japan.