Role-playing has long been a method in the professionalization of educators to emulate or anticipate everyday school and teaching situations. This paper introduces InCoLearn, the first multiplayer online role-playing game (RPG) developed for student teachers to facilitate professional and action-based knowledge of inclusion and heterogeneity in the classroom with non-linear storytelling through individual quests. A qualitative usability study conducted via focus groups aims to provide insights into usability. It seeks to answer the research question of which aspects are perceived as the most important and problematic to student teachers using InCoLearn. To answer another research question, whether previous quantitative usability results can be confirmed and explained by the qualitative results, the qualitative results are set into the context of a quantitative usability study.