Japan Times : Human-trafficking at record 79 cases but number more likely in thousands

Police either made arrests in or turned over to prosecutors 79 cases of alleged human-trafficking involving foreign women forced into the sex industry or other forms of exploitation last year.
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The cases are believed to be just the tip of the iceberg. Human rights groups and researchers estimate thousands of women, mostly from poor parts of Asia, are trafficked into Japan every year and forced to work in the sex trade.

Japan came under international pressure last year to combat human-trafficking after the U.S. State Department issued a report in June slamming Japan's efforts to crack down on the problem.

Tokyo subsequently adopted a plan to combat human-trafficking in December.

As Japan has no specific laws against human-trafficking, police have to use other laws related to immigration, prostitution, employment security and other areas to combat the problem.
That is part of my complain about Japan's legal system, but possibly due to different moral standards, namely that prostitution has always existed, is natural and necessary for the society as an outlet to violence for men. Maybe, but that doesn't mean human trafficking is justified and that there should be no law about it.