Story highlights Police said 54-year-old man used fake sleep study to drug, rape and film women

One woman said she saw herself in a video online

Local media has done little coverage of the crimes

(CNN) Police say around 100 women in Japan who thought they were participating in a sleep study were actually drugged and raped, their attacks recorded and sold to porn sites.

Authorities arrested 54-year-old Hideyuki Noguchi, after one of the women saw herself in a video online and came forward. Police investigated and arrested Noguchi, who has been charged with incapacitated rape, according to Chiba Prefecture Police spokesperson Satoshi Kono.

Authorities say Noguchi has told them the number of victims is about 100. Officers have confirmed at least 39 of those victims, and have filed charges in many of those cases already. More women could come forward.

The assaults allegedly began in 2012 when police say Noguchi took out a newspaper ad seeking participants for a sleep study. The ad sought women from their teens through their 40s and offered compensation for their time.

Noguchi would then arrange for women to meet him at a hotel or a hot springs inn, according to authorities. He would allegedly tell women he planned to test their blood pressure while they slept. He reportedly told women he was a doctor, but police could not confirm that.

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