A review on the developments of the magnetic-resonance-related spin chemistry in Japan is presented. We describe how studies in this area started in Japan and developed into the flourishing state of the present. Important contributions made by Japanese spin chemists in the last two decades in three areas, namely, work on chemically induced dynamic electron polarization, excited states and controlling of photochemical reactions, are presented. More emphases are placed on the new developments in recent years, particularly new concepts and new methodologies.