Although distance language education has been widely adopted in university learning, very few researchers to date have looked at off-screen behaviors of second/foreign language learners in their physical environments while they engage in synchronous (real-time) online courses. This study examined one focal student's off-screen behaviors while she worked in front of the computer in her physical environment during a university-level synchronous Japanese class. The class was mediated by audio-based conferencing software ("Wimba") where class participants' behaviors in their physical environments were not observable to others. The primary data consist of two types of video recordings that were synchronized in a picture-in-picture format: the focal student's off-screen behaviors in her private environment and archived online classes with instructor and seven classmates (~20 hours). Drawing on conversation analysis, the study showed unique characteristics of interactional norms developed by the student in her physical environment in contrast to those observed in a controlled online environment. The focal student's off-screen behavior suggested that she gained significant affordances from the course format; namely, opportunities to freely take her private turns by vocalizing the language "off-screen" without being heard. The study illustrates the potential of computer-based learning to promote increased learner agency and autonomy.