After an eight-day fact-finding mission in Japan, a UN investigator condemned the country's failure to address the sexual exploitation of children.

"We have many forms of sexual exploitation of children in Japan, many of which are not necessarily criminalized," said Maud de Boer-Buquicchio, special rapporteur for the United Nations on the sale of children, child prostitution, and child pornography. This includes the JK business in the country — JK stands for joshi kousei, or a female high school student — which involves a range of services, from photos of schoolgirls in sexually provocative attire to J__K o-sampo [honorable walks with high school girls] to sex services.

At a press conference at the Japan National Press Club in Tokyo on Monday, De Boer-Buquicchio said she had visited local governments, talked to victims and businesses alike, and been to shelters for sexually abused children. She pointed out that 13 percent of Japanese schoolgirls are involved in some form of enjo kossai [compensated dating]. She also noted the use of very young children in the production of erotica and the marketing of "Junior Idols" as unacceptable, though it's considered quasi-legal within Japan's borders.

Watch the VICE News documentary 'Schoolgirls for Sale in Japan.'

Some of the JK businesses are fronts for teenage prostitution and sex trafficking. Lighthouse Japan, an NGO that combats human trafficking, reports that often the girls involved in JK o-sampo walks end up in so-called love hotels with their older customers. De Boer-Buquicchio said these activities were "a very lucrative business" in Japan "which seems to be socially accepted and tolerated." She also noted that while Japanese police, working with non-profit groups, have worked to combat online child pornography, there was little long-term support for the young victims of sexual exploitation.

Last year, Japan amended the child prostitution and pornography law to criminalize the private ownership of what De Boer-Buquicchio called "child abuse material," or child pornography. But there was a one-year grace period granted for those possessing child pornography; some estimates said as many as 1 in 10 Japanese men owned or had seen child pornography. De Boer-Buquicchio said that of the few cases prosecuted, the convictions often result in suspended sentences or minimal penalties such as fines.

"Even if the criminals are convicted the sentences are extremely low… the whole atmosphere of impunity needs to change," she said.

In September, the Kyoto Cyber Crimes Unit arrested three men, including one university student, who allegedly used the Tor browser to upload 660 photos of child porn and other images to a private website. Police said users purchased images with Bitcoin. The police were able to track down the managers of the website via transaction records.

According to Japan's public broadcaster, NHK News, this was the first time a UN representative had come to Japan specifically to investigate the sexual trafficking of children and gauge the effectiveness of counter-measure being taken. The results of the investigation and her recommendations will be submitted to the UN Human Rights Council next March.

With additional reporting by Reina Marie Iino.