In mobile communications studies, Japan is known for its “keitai culture.” However, the actual use of keitai among the Japanese is anything but glamorous. On the other hand, strong preference of online diary and diary blogs among the Japanese is remarkable. What is puzzling, however, is that the Japanese online diarists and bloggers have been astoundingly self-effacing. What communications are they engaged in, with providing little information about themselves? Relying on and advancing the methodological perspective of “communicative ecology,” this study discusses the way online diaries and blogs are intertwined with mobile communications, embedded in the communicative ecology. It also reveals the way “kuuki wo yomu” (read the atmosphere) motivates people's expectations and actions in social communications, contributing to the formation of the communicative ecology.