The development of astronomy has been developed by the cooperation of amateur astronomers and researchers. Sunspot observation is a good example of Extreme citizen science in early days. Issei YAMAMOTO (1889–1959), organized “Oriental Astronomical Association (OAA),” Yamamoto’s materials (now in Kwasan observatory) include solar observation data sent from many observers in Japan. From the viewpoint of today’s Citizen Science, collaborative observation of sunspot between researchers of solar physics and amateur astronomers in Japan has clearly a context of social mission rather than mere academic interest. From the viewpoint of science communication, we can see that Yamamoto’s call includes a social mission to promote astronomy in Japan, and that amateurs responded to Yamamoto’s call by participating in the observation network. It can be said that this collaboration have not only “cultural” aspect but also “civic”or “practical” aspect.