The Japanese host. You can see them on the streets of Tokyo’s Kabukicho: the dapper thin men with colored, blown-dry hair, fake suntans, snazzy suits and charming smiles, chatting up passing females and trying to get them to come and have drinks. They’ve been the subject of documentaries, television series and popular manga such as “Shinjuku Swan.”

Host clubs are the male version of a hostess club. The office ladies, college students, housewives and women involved in the “water trade” (hostesses, cabaret girls, strippers, sex workers) come to them, and the male hosts give them a “boyfriend experience.” They flirt with them, pour drinks, light their cigarettes, sometimes dance with them. Part of the game is to convince the women to open an expensive bottle of Champagne, for which they get a drink back (or a percentage of the charge). If the women become fans of a particular host, they try to spend more so that their man can become the No. 1 host — the Shorty Award of host life.

It’s all fun and games — but not really. The bills the female customers rack up can amount to tens of thousands of yen and when it comes time to pay, suddenly the hosts aren’t so charming anymore. In fact, some host clubs use the debt racked up by the women to subtly — and sometimes forcefully — make them work as prostitutes. It’s a business.

Host club owners have the set-up down pat. Many men who run host clubs also have some kind of brothel or other adult entertainment establishment, where they put to work club patrons who can’t pay their tab. There’s a venue for every type of woman, and she may have a choice of how she wants to work off her debt.

Host clubs are usually an over-18 affair and ID is required at most venues. However, some enterprising “businessmen” will pull in younger girls on purpose, and let them run up a tab — before they spring them with a bill they can’t pay. Sometimes they’ll blackmail the teenagers by threatening to go their parents for the money. Host clubs may be owned either by the yakuza or by yakuza associates. The club’s employees often fall somewhere in between.

In late February, the Metropolitan Police Department busted the manager of a host club in Ikebukuro on charges of violating the prostitution law. Police arrested Manabu Fukushima, the 30-year-old manager of a club called A-Amemba, his brother, his 51-year-old mother and six other suspects for allegedly forcing several women into prostitution between Oct. 30, 2013, and January.

Fukushima is accused of forcing a 20-year-old woman to perform sexual services for at least four men at love hotels in the greater Kanto area. She reportedly had racked up a debt of ¥1.25 million. When she tried to quit and run away, Fukushima allegedly hunted her down, beat her and then threatened her. “Because you can’t pay, you can either cut off one of your fingers or work as a hooker to pay it back,” he allegedly told her after the beating. He did not touch her face — that would have damaged the goods.

The woman had worked for the host club for a month but the accused claimed she’d only paid off the interest on her debt. The mother of the manager and his family reportedly kept the women in confinement at their home. The victim eventually obtained a mobile phone and contacted her own mother, who in turn called the police. The accused reportedly earned ¥2 million from her exploitation, far more than her debt.

Other female victims claimed they were paid ¥5,000 to ¥30,000 per male customer and when it looked like they had repaid the debt, they were summoned to events that looked for all intents and purposes like host “birthday parties” and charged as much ¥470,000 for the privilege, thereby kept as perpetual debt slaves.

However, this isn’t the first time cases like this have happened. According to the Asahi Shimbun, a host club owner in Hyogo Prefecture lured a 15- and 16-year-old girl into a host club in 2004 and let them rack up a bill they couldn’t pay. The owner then sold them for $10,000 to a brothel bar owner. They were kept captive in an apartment and forced to have sex with an estimated 200 customers in two months before being rescued by the police. The traffickers were both charged for violations of the law banning child prostitution.

In 2007, the police arrested a host club owner who had forced a 20-year-old female to work off her ¥500,000 bill in a brothel located in Taito Ward.

I have been working with the nonprofit organization Lighthouse: Center For Human Trafficking Victims Support (formerly Polaris Project Japan) and victims have reported similar cases to us since 2008.

“There are many means available to effectively enslave women in Japan — blackmail, threats, debt or fraud,” says Lighthouse representative Shihoko Fujiwara. “In many cases, the host club doesn’t directly control the women. They introduce them to affiliated loan sharks who handle the ‘pay back’ to the club and then the women work off their debt at sex clubs introduced by the loan shark. Behind the scenes, they’re all working together but proving that it is a genuine case of human trafficking is difficult.”

Awareness of human trafficking is low, even among law enforcement agencies, Fujiwara says. Lighthouse trains immigration officials and police officers to recognize victims, but punishing the culprits isn’t easy. “Japan has a tough human trafficking law but it’s rarely applied because the hurdles are high,” she says. “If Japan really wants to stop trafficking, they need to interpret the laws more broadly or revise them.”

The penalty for violations of the human trafficking law in most cases are between one to 10 years in prison. Those found guilty simply can’t get away by paying a fine. For violations of the prostitution law, the maximum sentence is less than 10 years in prison or a fine of ¥300,000. Law enforcement sources say people found guilty of prostitution charges usually receive a fine and serve no prison time.

Even silly-looking hosts know how to do cost/benefit analysis.

Dark Side of the Rising Sun is a monthly column that takes a behind-the-scenes look at news in Japan.