This chapter analyzes the “barrage subtitling” (danmu) practice in the Chinese video sharing site Bilibili, in comparison with the practice in the Japanese site Nico Nico Douga. Barrage subtitles—danmaku in Japanese—are a subtitling system originated in the Japanese video sharing site, in which viewers’ comments appear directly onscreen instead of at the margins. They differ from ordinary subtitling, which is usually well prepared in advance for the purpose of precisely translating the contents of videos—whether they are a film, a TV program, or a music video. Because barrage subtitles are comments and reactions to what is being played, they allow more spontaneous interactions—what sociologist Georg Simmel called “sociability”—among the viewers. Moreover, in the communicative practice of barrage subtitling, the purpose of interaction is not solely the conveyance of substantive meanings, but the continuation and proliferation of communication. Here again, Simmel’s distinction between “form” and “content” becomes useful. Put differently, in order to capture the nature of youth cultures and collective spaces in cyberspace, how Millennials communicate is as important as what Millennials communicate using the video sharing sites such as Bilibli.