Naikan was very popular among Japanese prisons as an effective correctional treatment between 1954 and 1964. However, there is no prison, which has introduced Naikan, now. The purpose of this research is to solve the cause of Naikan decline in the prisons.
So I analyzed both Mr. Yoshimoto’s activity for Naikan in the prisons and correspondence of the prisons to a time series. As a result, the cause is that semantic element about Naikan in the prisons had changed. And more, it turned out that prison officer’s Naikan was different from Yoshimoto’s original Naikana about interview.