Japan’s police have busted a voyeurism ring that filmed thousands of women bathing in hot springs across Japan for over 30 years.

Police in Shizuoka prefecture have arrested 16 men in a breakthrough that came a little more than a year after the arrest of the alleged ringleader, 50-year-old Karin Saito, reported The Asahi Shimbun newspaper.

Mr Saito, who was arrested in December 2021, identified more than a dozen men who he said filmed and shared explicit images and videos of women bathing in hot springs.

The arrests were made earlier this month and the accused include senior company executives, local government officials and a doctor from Tokyo.

They are accused of violating nuisance prevention ordinances, a law against illicit photography and pornography. They are also suspected of violating child pornography laws.

Mr Saito confessed to committing voyeurism in at least 100 locations when he was 20 years old.

The men who were arrested learnt techniques of voyeurism from Mr Saito, known as “a charismatic voyeur” in the network, and used high-end technology to film at least 10,000 women, investigators said.

They used to take pictures and videos of the women in hot springs while hiding several hundred metres away in the mountains.

High-quality video and photographic equipment, including telephoto lenses, were used by the group. The men created videos and added subtitles to them as well.

They would also hold get togethers to screen the videos.

The news of the arrests has sent shockwaves through the country’s hot spring community, that attracts millions of domestic and international tourists every year. It has raised fears that the news will badly impact an industry that was getting back on its feet after being hit by the Covid pandemic.

“This is shocking and I have to say that voyeurism for the purpose of obtaining naked images of someone of the opposite sex simply has to be severely punished,” said Yutaka Seki, executive director of the Japan Hot Springs Association, told South China Morning Post.

He said new technology, such as miniaturisation of cameras, has made it difficult to enforce strict rules of illicit and unauthorised photography in hot springs, also known as onsen.

“It’s quite disturbing,” Hiro Miyatake, founder of the Bear Luxe Corp network of travel companies told the outlet.

“An onsen is meant to be a place where anyone can go and be completely relaxed. It’s an important part of Japanese culture and something that all foreigners want to do while they are visiting, but incidents like this can seriously hurt that image.”

Mr Saito was caught under nuisance prevention ordinances for reportedly drugging women with sleeping pills and committing indecent acts at his parties.