In this study, we'd like to report on the development of 2-year-group therapy for a high school boy who has had a tendency of autistic spectrum disorder (ASD). The high school boy had a problem of interpersonal communication peculiar to ASD, and had a difficulty in making good relationship with others in his school life. Also, in the group activities, he was far too immersed in his favorite activities that he paid little attention to other members. In a group therapy, he made up a "client's project" in which he himself organized a session and positively utilized his persistence to his favorite activities. In the process of devising the program, he discussed with the therapist in charge and the leaders what kind of ideas would be required for other members to enjoy the activity as well. In the discussion, he reviewed his program so that every member can enjoy it as well as him and made some adjustments to the content of the program. In conclusion, it would be possible to promote ASD people's awareness of others by understanding their persistence to the objects, which can be their strength, and utilizing it positively.