Of persons sentenced to imprisonment with or without labor, those under 20 years of age at the time of trial are referred to as juvenile prisoners. Sentences for juvenile prisoners are executed in juvenile prisons or specifically designated sections in prisons, to prevent adverse influences from adult prisoners and ensure sufficient education and training. Execution of sentences can be continued in the same prisons until juveniles reach the age of 26 even after they reach 20. Juvenile prisoners who are under 16 years of age can be treated at juvenile training schools until they reach 16, in accordance with a partial amendment to the Juvenile Law, effective as of April 1 of 2001. All convicted juvenile prisoners in 2001 were 16 years old or over.
  As of April 1, 2002, 8 juvenile prisons have been established, in Hakodate, Morioka, Mito, Kawagoe, Matsumoto, Himeji, Nara, and Saga.