In Japan, calls for students to become global human resources (GHR) has placed pressure on universities to internationalise. Traditionally, Japanese universities have relied on student mobility to foster GHR, but a decline in mobility numbers has highlighted the need for educators and administrators to consider how an intercultural mindset can be developed in domestic campuses. While English as a foreign language (EFL) education holds great potential due to its widespread, mandatory status across Japanese universities, it remains underexplored, particularly under the curriculum restraints often faced by EFL faculty. This article will present results from a one-year longitudinal study conducted with 205 EFL Japanese university students in the 2021 academic year, during which intercultural activities were incorporated into the curriculum. The article will discuss the factors influencing students' openness, curiosity, and respect, as well as cultural self-awareness and global awareness based on pre-, mid-, and post-intervention surveys, in addition to student reflections collected from 41 participants. Findings suggest that EFL classrooms have the potential to develop an intercultural mindset despite curriculum constraints, particularly through guided discussions in the classroom and student-led research projects with an intercultural focus.