Some scholars have proposed that in principle, there is no need for the Interviewer in Naikan. To test this assumption, the authors undertook their own experience of Intensive Naikan Therapy without an Interviewer, through which we realized the necessity of the Interviewer. In this study, we set out to understand the importance of the Interviewer’s role in Intensive Naikan Therapy from the perspective of clients. We conducted semi-structured interviews with 13 clients after an Intensive Naikan program, and analyzed their narratives using a method called Grounded Theory Approach (GTA). All of the clients who were interviewed considered the interviewer necessary for the therapy to be successful, and their reasons were classified into 6 categories, which we discuss. Their replies also suggest that the presence of a single Interviewer enhances the client’s experience of Naikan, while a plurality of Interviewers seems to increase the patient’s psychological burden.