The goal of this study is to contribute to the field of Japanese pedagogy by examining how Japanese native speakers and learners of Japanese as a foreign language with American cultural backgrounds take stances in discussions in Japanese. As stancetaking is a fundamental human behavior (Du Bois & Karkkainen, 2012; Iwasaki, 2015; Kiesling, 2022), learners of foreign languages inevitably experience stancetaking moments in the target culture. Investigating stancetaking in the context of cross-cultural discussions is meaningful because the ability to negotiate in multicultural environments is critical in a world that aims to cooperate with people from different cultures (Jian, 2021).Although how native speakers of Japanese express opinions and manage confrontational moments have been studied by a number of scholars (e.g., Watanabe, 1993; Mori, 1999; Noda, 2004), how learners of Japanese manage disagreements from the perspective of stance and stancetaking have not been investigated yet. This study explores how native speakers of Japanese and learners of Japanese at different proficiency levels negotiate stances when they manage disagreements. The research question of this study is: How do native speakers of Japanese and learners of Japanese at various proficiency levels take stances when they face contrary opinions in discussions in Japanese? Based on the answers to this question, it further argues the difference between native speakers' and learners' stancetaking in discussions, the learners' acquisition process of stancetaking, and probes the effective ways to guide learners to take stances in discussions. To investigate stancetaking in discussions by Japanese native speakers and learners of Japanese, data were collected from one-on-one mock discussions, reflections of those discussions, and questionnaires from ten subjects: two native speakers and eight learners of Japanese who are in levels 3, 4, and 5, and beyond level 5 of Japanese courses in the university level. The data from the mock discussions demonstrate that the speakers utilize various stancetaking strategies when managing contrary opinions. It also manifests different traits in terms of stancetaking behavior between the native speakers and the learners. The difference is especially significant when the native speakers and the learners beyond level 5 are compared. The native speakers constantly seek their common ground or commonality at a personal level through active alignments, suggesting that they build a personal connection by empathizing with each other. By contrast, the beyond level 5 learners take stances by acknowledging both Japanese and American cultures and expressing how their stance differs depending on the culture, which indicates that their stancetaking strategies are not a simple copy of native speakers. This finding illuminates the significant potential for what the learners of foreign languages can offer in discussions. Furthermore, the reflection sessions and questionnaires reveal learners' struggles in expressing their opinions against contrary opinions because they consider it goes against their Japanese culture theme compiled through their experiences of learning Japanese. This finding suggests the importance of teaching practical strategies of stancetaking in disagreement management in classrooms and promoting the learners' awareness of Third Space so that they can negotiate and cooperate with people in the target culture by taking advantage of their multicultural backgrounds. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]