The adoption of English-medium instruction degree and non-degree programs in non-Anglophone universities has grown dramatically over the past 15 years. Japan is not an exception. In the Japanese context, a growing number of research works have addressed the implementation of English-medium degree programs at the undergraduate level; however, little has been done to address this implementation at the graduate level, especially from a bottom-up perspective. This study addresses this gap in the research through a mixed-method study of two Japanese leading universities. Results revealed a fairly good on-campus satisfaction of English-speaking graduate international students. However, it showed that the current university support system has been mainly relying on the informal support of supervisors, international student support office staff and/or student tutors, while there has been a lack of formal university support, especially regarding the monolingual and monocultural (Japanese) administrative infrastructure. Through a double hermeneutic interpretation of the study data, possible rooms for on-campus support improvements are discussed. Results show that, with the ongoing increase in the number of English-speaking graduate international students in Japanese universities, more systematization and formal support would be needed.