Approximately 6.5% of Japanese students have a possible diagnosis of a developmental disability and are enrolled in regular classrooms in elementary and junior high school (MEXT, 2012a). There is a limit to a teacher’s ability to resolve the issues faced by students with developmental disabilities given current classroom practices (or conditions), so many teachers are concerned about their ability to manage these challenges. To better support students with developmental disabilities, improvements that lead to increasing understanding and support from typically developing students surrounding students with developmental disabilities is a possible solution. Thus, it is important for students with developmental disabilities to have a comfortable learning environment in order for these students and non-disabled students to learn together in a regular class. It is not enough just to structure the environment of the classroom or to provide reasonable accommodation. It is necessary that the classroom atmosphere, classroom discipline, and classmates have mutual respect. In Japan in particular, in addition to pursuing a comfortable learning environment with UDL in order to tackle various activities for one year with the same member (classmate), it is important to maintain a warm atmosphere.