The careful use of online learning can achieve a variety of goals in sustainable education, such as providing access for students, particularly in times of crisis, as well as providing them with opportunities to study interdependently. Also, it gives them the opportunity to develop thinking skills and awareness to become active in working towards sustainable societies, ones where the actions of the current society do not damage the abilities of future generations to address their own needs. In this small-scale study at a Japanese national university, the switch from classroom-based teaching to online study in language education is considered in relation to flipped learning. This involved videoconferencing software and the organization of "study buddy" groups, supported by materials on a learning management system. The effect of the change has been investigated using a mixed-methods approach with survey data from students and data from two classroom observations by external observers. The data has been analyzed and framed in relation to sustainable education goals, produced by Japan's Ministry of Education, Culture, Sports, Science and Technology (MEXT), such as cooperation, interdependence, sense of responsibility, and international awareness. The author of this study found that the flipped learning approach was successful in building an online community and social interaction that provided the framework for achieving education for sustainability. In conclusion, the author considers how hybrid courses involving both classrooms and online technology may be the future for English language courses in Japanese universities.