Telecollaboration involving children around the world allows them to develop international understanding (IU). This paper reports on the design and implementation of a telecollaboration project between Japanese and Australian primary school students. The main purpose of the project, which integrates the contents of Social Studies and foreign language (FL) education, is to promote student interest in learning their own and a foreign language, as well as a foreign culture, using an educational social network site (SNS), in this case Edmodo. This study focused on Japanese students in particular. The exchange of cultural information online became a meaningful and authentic activity for communication in FL. Additionally, the evaluation showed that the Japanese students became more motivated to learn English and initiate IU. A curriculum-based telecollaboration project involving a long-term plan -- instead of a one-off activity -- is recommended in order to develop young students' IU in FL education.