Be VERY careful about this.
Labor laws here.
http://www.jil.go.jp/english/laborinfo/library/documents/llj_law1-rev.pdf
Start with p.42 (article 56).
(Minimum Age)
Article 56. An employer shall not employ children
until the first 31st of March following their having fully
reached the age of 15 years.
2. Notwithstanding the provisions of the preceding
paragraph, outside of school hours, children above 13 full
years of age maybe employed in occupations in enterprises
other than those listed in items 1 through 5 of Annexed
Table No. 1, and which involve light labor that is not
harmful to the health and welfare of the children, with the
permission of the administrative office. The same shall
apply to children under 13 full years of age employed in
motion picture production and theatrical performance
enterprises.
[Look at the end of this file for the Annexed Tables. Glenski]
immigration,visa,Japan
Also, pay heed:
Article 58. The parent or guardian shall not make a
labor contract in place of a minor.