This contribution attempts to clarify the relationship between the practice of plurilingual education and STEAM (interdisciplinary pedagogy that incorporates science, technology, engineering, art, and mathematics) through the lens of peace learning at an elementary school in Japan. Japan has a rich history of peace education, although it has received limited focus in the international literature, whereas plurilingual education remains relatively unknown in the country. Within this context, the article examines a teacher-initiated plurilingual and intercultural project focused on a multidisciplinary approach to peace learning. Analyses of multimodal data, including video recordings, photographs, researchers' field notes, learners' journals, and semi-structured reflective interviews, will demonstrate how even within a highly homogenous context, practitioners can promote transferable skills and nurture a deeper awareness of language and openness to diversity, foster reflexivity, and encourage multidisciplinary engagement through plurilingual education, dialogue, and storying.