Japan has had a problem with younger girls doing "things" for gifts for a long time. It is called enjo kosai, which translates as "assisted dating" or "dating for assitance".
See:
http://www.belmont.edu/philosophy/courses/.../EnjoKosai.html
Basically, japan has only very recently passed laws regarding sex with girls under 18, and they only really apply to Gaijin anyway (foreigners). They do not have the western Christian anti-sex moral stand, and as a result, the sex industry is very open and honest in Japan, including date lines - which are really nothing more than facilitators of freelance prostitution.
Alex