The essence of treating inmates in correctional institutions lies in giving correctional treatment throughout the execution of the sentence and aiming for the reform and social rehabilitation of the inmates. The basic systems for the treatment of inmates are the Classification Treatment System and the Progressive Treatment System. There is also an Open Treatment System, implemented in accordance with the character of the inmate.
(1)Classification Treatment System
  To aid the reform and social rehabilitation of inmates, treatment must take account of the personal characteristics of individual inmates, as well as environmental and social problems. Scientific surveys conducted in order to ascertain the problems of individual inmates are called classification surveys. Treatment plans are drawn up on the basis of these, groups of inmates are formed with a view to implementing these plans effectively, and effective treatment is then carried out in line with the nature of the group.
(2)Progressive Treatment System
  The Progressive Treatment System was created as a way of encouraging inmates to make efforts to reform themselves. Four grades (Grades 1 to 4) have been created throughout the course of execution of the sentence. Inmates gradually progress from the bottom grade (Grade 4) on initial admission, depending on their performance. They are, accordingly, given increasing privileges and restrictions on their freedom are eased, bringing them closer to normal social life. At the same time, by giving them ever greater responsibility within communal life, their social aptitude is improved.
(3)Open Treatment System
  The Open Treatment System is a form of treatment whereby the degree of confinement, in terms of the physical facilities of the institution as well as human measures, is reduced on the basis of trust of the inmate's self-discipline and sense of responsibility. This treatment is implemented in correctional institutions housing traffic offenders and female inmates. Some open treatment is implemented in the form of external work in locations such as the Masukawa Farm(attached to Hakodate Juvenile Prison)and the Oi Shipyard(attached to Matsuyama Prison). In institutions offering open treatment, inmates'cells, canteens, workshops, and other rooms are in principle kept unlocked. Prison warders are not assigned to the penal area, while prison visits are conducted without guards as far as possible. Lifestyle guidance, occupational training, and other educational treatment necessary for social rehabilitation are implemented positively.