First there were the "enjo kosai" Internet sites where underage girls hook up with adult males in exchange for money. Now there's a new type of Web site that unites girls running away from home with men offering a place to stay in return for sexual favors.

Called "iede saito," or runaway sites, and potentially harmful to children, they provide a forum where messages posted by runaway girls asking for a place to stay are answered by men.

Observers say such sites have emerged because the operators and male users want to dodge new laws on "deaikei," or "encounter sites" (where members of the opposite sex can meet), that ban people under 18 from using them, diminishing the chance they will attract underage girls.