Among penal institutions, prisons and juvenile prisons house those offenders sentenced to imprisonment with or without work and misdemeanor imprisonment without work and provide necessary treatment for them. Detention houses mainly house untried inmates (persons arrested or detained or those detained who have not yet been tried and sentenced; hereinafter the same). Penal institutions have workhouses in which offenders who are unable to pay fines or petty fines are detained, and except for some institutions also have houses of Kanchi confinement in which persons subject to confinement as the punishment for contempt of court (Kanchi confinement) under the provision of Article 2 of the Act for Maintenance of Order in Court-Room (Act No. 286 of 1952) etc. are detained.
  The Act concerning Penal Institutions and Treatment of Sentenced Inmates (Act No. 50 of 2005; hereinafter referred to as the "Inmates Treatment Act") was enforced on May 24, 2006.
  As of April 1, 2006, with regard to penal institutions (meaning "prisons" before the enforcement of the Inmates Treatment Act; hereinafter the same), there were 74 main institutions (59 prisons, eight juvenile prisons, and seven detention houses) and 113 branches (six branch prisons and 107 branch detention houses).