TOKYO — The Kyoto Police have taken down a legendary pervert. In Japan, the term for such people is chikan—men or women who grope, fondle, leer at, or otherwise sexually harass the opposite sex in public, usually on mass transit, like trains, subways, or even late-night buses.

This chikan was known all over western Japan as Chikubi Ojiisan, “The Nipple Geezer” or “Mr. Nipples.” For the many women—possibly hundreds—who’ve had to endure his penetrating stare on the train while he played with his nipples, his arrest is welcome news.

But playing with your own nipples in a public place, if you’re a man, is not technically illegal. And this guy, in many cases, did not even take off his undershirt.

So his rather strange but apparently numerous “fans” are wondering why he finally crossed the legal line, which is basically, well, below the belt. The arrest has also reignited a debate in Japan about just what is “obscene.”

It’s the kind of question the Japanese find at once irresistible and insoluble when it comes up outside the conventional norms of porn. In the summer of 2014, for instance, the Tokyo Police were heavily criticized for the arrest of a “vagina artist” who produced, among other objets d’art, a vaginal kayak.

Nobody ever claimed “The Nipple Geezer” was an artist, but he certainly managed to attract a lot of attention in the regional press. His first appearance on social media was in July of 2013. A woman tweeted, “This jerk, is playing with both his nipples while staring at my face. The way he stares—it’s creepy, right?” She posted a photo of him in a white T-shirt.

Other victims followed with their own posts. The general opinion was that he was creepy but, one hoped, harmless. Women warned each other to be careful. Despite his youth, he was referred to as “ojisan” meaning literally uncle but sometimes used as a pejorative term for middle-aged men, or sometimes simply “mister.”

The National Police Agency did a survey in the summer of 2010 that found 13 percent of Japanese females had experienced sexual harassment, including groping in the transit system—within just a one year period— but 89 percent of the victims did not complain to the police.

The National Police Agency interviewed the victims, who responded that they didn’t know where to complain or whom to speak with. Some felt that their complaints wouldn’t be taken seriously. Other transit police departments in Japan have found that roughly half of all women had encounters with a chikan.

Unless the gropers directly touch the women or go too far in exposing themselves, there is a limit to what the police can do. In Saitama Prefecture, groping during the morning rush hour is such a social problem that there are “Women Only Cars” to prevent the crime and police urge local women to use them.

Some police departments in Japan last year began distributing double-layered “chikan prevention stickers.” The first layer says “Don’t touch me,” and is to be shown as a warning. The second layer can be used to mark the molester with permanent ink, so he can’t escape.

However, these stickers also provoked cries that they could be used to frame someone falsely. There certainly have been cases where men accused of the crime turned out to be innocent but only after being put through the meat grinder that is Japan’s criminal justice system.

That said, while there may be false accusations the biggest problem is that still roughly 90 percent of the cases go unreported and many offenders know the legal loopholes that will let them stay out of jail.

For almost three years, the Nipple Geezer managed to avoid breaking the law while he continued to creep out the women he set his eyes on. He seemed to enjoy the expressions of disgust and dismay that he caused to younger women, especially high school girls. He even wore customized white T-shirts in which he had cut small circles to fully expose his nipples.

Finally, on June 5, detectives from the Kyoto Police Joyo Station arrested Toshihiro Fujikuma, 33, an employee of Shiga Prefecture Ritto City, on charges of public indecency.

According to the police, on May 21 at 6:45 p.m., on the Kintentsu Kyoto train line in a car heading to Terada Station, he exposed parts of his body in front of several high school girls, and others, thus breaking the law. One of the victims consulted her mother, and the two went to the Joyo Police station and lodged a complaint.

At the time he was arrested, Fujikuma did not state his real job, insisting that he was a supermarket employee. It was later discovered that he held a position in the social welfare section of Ritto City’s health and welfare division. He was a case worker, assessing the needs of those needing welfare payments. He told the police that his behavior on the train was his way of relieving stress.

Ritto City officials told The Daily Beast, “He was a very hard, dedicated worker and we’re shocked.”

The city even set up a web page to address the issue, stating: “We are very sorry that one of our city employees caused such an incident and deeply apologize. We will strive to regain the confidence and trust of the citizens in the future and take harsh measures.” The city officially fired him on June 27.

The Kyoto Police believe that Fujikuma has been guilty of several other acts of public indecency. The Kyoto prosecutor’s office agreed to let Fujikuma be freed on bail last week, while the investigation continues.

It is not clear why Fujikuma “crossed the line” from exposing his upper body to his lower body, but there’s not much question the Kyoto Police were on his case, looking for him to make a mistake.

The Kyoto Police, despite being one of the smaller forces in Japan, are well known as a progressive and fearless department, aggressively enforcing Japan’s anti-child pornography laws, even during the period (up until 2014) when simple possession was still legal. In 2010, they also managed to arrest Kiyoshi Takayama, the former second-in-command of Japan’s largest crime group, The Yamaguchi-gumi, on extortion charges; he was later found guilty.

One notable characteristic of the Kyoto Police is that they have a higher than average number of female officers, and they are very proactive handling crimes against women. Many police departments don’t take a very serious approach to the problem, simply distributing ineffective warning posters and pamphlets. There is even a Twitter account devoted to looking at the chikan crime prevention posters and how they often fail to even communicate what constitutes the crime.

In May of 2014, Kyoto appointed a woman as the head the Kyoto Railroad Police Squad for the first time in the history of the Kyoto.

In March of 2015, in an unusual move, the city designated 29 police outposts to be staffed 24 hours a day with female officers. The reason: to better respond to female victims of stalking, domestic violence, groping and other crimes, who might feel a male police officer would be unsympathetic or hard to approach.

They have implemented some of the recommendations of the National Police Agency and made it clear that sexual harassment of women or obscene behavior in public won’t be tolerated. They have even held contests seeking the best prevention poster. They have put the posters not only in train stations but local business offices as well. The Kyoto Police don’t consider harassment of women a laughing matter.

Arresting The Nipple Geezer, despite the ludicrous name, is one way of showing how serious they really are.