This paper investigates how web services for real-time communication influence formulation of a community. Since live streaming services with simple equipments become available, more and more events including conferences and workshops are broadcasting recently. Microblog services along with the live streaming also activate online communication among members of the event. We assume that such the web services play an important role to maintain sustainable growth of the community. To observe interaction among members of the community during their holding event, we collected tweets which relate to the event and analyzed them. Our findings so far are as follows; (1) acquiring certain amount of new participants constantly is important, (2) beginning organizers tend to have an experience of attending previous event of the community via live streaming and/or on site, and (3) several key participants to propagate the event's activities exist both on site and off site.