In the children's book Sadako and the Thousand Paper Cranes, a 12-year-old girl who had been living close to ground zero when the atomic bomb was dropped on Hiroshima in 1945 is diagnosed with leukemia and given a short time to live. So she begins folding paper cranes; in Japan, it's said that if you fold 1,000 of them, you will be granted a wish.

Sadako folds the cranes in the hope that she will live if she completes the task — but she dies before she's able. The book is based on a true story.

Recently, however, paper cranes became a symbol not of hope, but of the exploitation of teenage girls. In May, Tokyo police arrested three men for operating a business in the Ikebukuro district that allowed male customers to watch teenage girls fold paper cranes in their underwear, the Sankei Shimbun reported. The club, which was called Kurione, had two underage girls on staff when police raided it.

Customers could sit in a semi-private room containing a so-called magic mirror that allowed them to see up the skirts of girls as they constructed the cranes. The entry charge was $40 for 40 minutes, but customers could request a specific girl to watch for about $8 per five minutes. According to police sources, the shop also offered customers the opportunity to go to a private room alone with a girl, where she would perform sex acts for money.

The raid on Kurione was the latest in the police's battle against Japan's booming JK business. JK stands for joshi kousei, or a female high school student — though some businesses also exploit teen boys. VICE News investigates JK culture in the documentary Schoolgirls for Sale in Japan.

Watch VICE News' '**Schoolgirls for Sale in Japan.'**

One of the more common services is JK o-sampo, which translates as "honorable walks with high school girls" in which customers pay to go on a stroll with a Japanese teenager. Often, those strolls end up in a so-called love hotel; many of the JK businesses are fronts for teenage prostitution and sex trafficking.

"I don't know why men go so crazy for JK — maybe because we seem helpless, or maybe they can't handle women their own age," says Lisa, a 19-year-old bartender who talked to VICE News on the condition that we not use her real name. She works at a type of hostess club called a "girls' bar" in Setagaya-ku. By keeping girls behind the counter — most of the time — girls' bars manage to evade adult entertainment laws and stay open all night.

When Lisa was 16, she would stand outside of a "maid café" in Akihabara and wait for men who wanted the JK experience to ask her on dates. Maid cafes cater mostly to male customers and sound like what they are — places where women are dressed in sexy maid outfits. They often call the customer "master." Lisa, who would stand outside the cafe but didn't work at it, says she would simply dress sexily.

The men who approached her varied in age, from those in their early 20s to some who were as old as 80. They'd generally buy her dinner or take her for a walk. For this, she earned between $40 and $80 an hour. Some would want to buy her panties, which she would sell them for about $100; she always packed a few pairs. She lived with her mother on the outskirts of Tokyo, and Lisa says they didn't have a lot of money.

She'd work after school and on weekends, and she says she never had sex with the men. She didn't tell her friends about what she was doing.

"I didn't do it because I was stupid," she says. "I thought I was smart — and the money was so much better than anything I could get doing a part-time job."

When she was 17, a man in his early thirties took her to dinner and bought her drinks, then suggested they go to a love hotel to sing karaoke — he said he'd pay her more for her time and assured her they wouldn't have sex. But when they got to the hotel room, he closed the door, pinned her down, and raped her. While she was crying afterward, he took her phone and wrote down her number and took ID out of her wallet.

"He dared me to go the police," Lisa says. "He said, 'You can go to the police and say whatever you want, and I'll tell them you're a little whore. That I didn't pay you anything, and you're shaking me down. And then you'll go to juvenile prison for being a teenage prostitute.' I was so furious and I was so scared. I was the victim, but he was right — I didn't want to call the police."

JK businesses are seldom raided by authorities. What most of them ostensibly do is perfectly legal — talking to teenage girls is not a crime. The JK business includes "junior idols" who pose for photos with men at public photo shoots and release DVDs; some of the girls are as young as 13.

The influence of JK culture is hardly limited to society's fringes. Last month, a demo made for Sony's Project Morpheus virtual reality headset featured a young Caucasian woman wearing short shorts and a see-through sweater asking the user if he could teach her Japanese and become her sensei.

The tolerance for JK business also arguably extends to AKB48, an enormously popular all-girl "idol" group. (Idols are young starlets who are singers, actresses, models, and TV personalities, and whose public personas emphasize a girlish cuteness.) The frequently rotating members — AKB48 has as many as 88 at a time, all ranked according to their popularity with fans — sing pop songs with provocative lyrics and pose on magazine covers in bikinis.

Members are forbidden to have sex or date. In 2013, one of the girls, Minami Minegishi, shaved her head to express how sorry she was after she was caught spending a night with her boyfriend. The group reportedly made more than $128 million in 2013. By March of 2014, the group had sold a total of more than 30 million record albums. In December of the same year, the group set a record in Japan by selling more than 30 million singles.

Japan's largest newspaper, the Yomuiri Shimbun, had an AKB48 section in its "Children's Newspaper."

AKB48 is the brainchild of Yasushi Akimoto, who had previously enjoyed success with the all-girl band Nyanko Club — which translates to Pussy Club. Akimoto founded AKB48 in 2004 with the idea of them being "idols you can meet." He said that his goal was to create an accessible idol group which, unlike others that played only occasional shows, would perform regularly in its own theater. The AKB48 Theater in Tokyo is now a mecca for their fans.

Akimoto is touted as an entrepreneur by Japan's entertainment industry. Kaori Shoji, a veteran Japanese journalist, called him by another name in a 2014 piece in the Japan Subculture Research Center:

Yasushi Akimoto is what 50 years ago many older Japanese would describe as a Zegen, or merchant who dealt exclusively in young women. A Zegen was the middleman who bought and sold girls (often with the express consent of the parents) to the sex trade and entertainment industry. The [Allied command occupying Japan after World War II] also did much to stomp out the Zegen operating in and around Tokyo, but the middlemen simply went on doing what they did, and took on another name: "entertainment producer." From sex shows and strip houses to brothels and the euphemistically called "bars," the Zegen had their fingers in all the right pies… and kept the best for the entertainment industry, which had a direct pipeline to the yakuza.

Akimoto and his partner, Kotaro Shiba, founded the management firm of Office 48 in 2004. Part of the start-up capital allegedly came from the Yamaguchi-gumi Goto-gumi (now Rachi-gumi) crime syndicate, which controls large sections of Tokyo. In May 2013, the weekly magazine Shukan Shincho published an expose on AKB48 management and its connections to organized crime. It included a 2003 picture of Shiba with yakuza members and associates. In the picture, he is standing next to the wife of yakuza boss Tadamasa Goto.

According to the article — and confirmed by VICE News' police sources — Shiba had worked as a loan shark for a yakuza-backed firm earlier in his career. Police sources said that Akimoto associated with yakuza members until the fall of 2008.

Though Office 48 may have initially enjoyed mob financing, it is now part of the Japanese entertainment landscape, where periodic attempts to purge the yakuza almost always end in failure.

Akimoto also serves as an advisor to the 2020 Olympic Committee and is on the government body devoted to promoting Japanese culture, the "Cool Japan" Commission.

Though the top AKB48 stars can earn millions, many others earn less than $10 an hour. Many girls who had "graduated" from the group — in other words, been fired — have ended up in the adult film industry. But AKB48 is such a cash cow for the Japanese entertainment industry that few dare to put Akimoto on the spot. In a disastrous 2012 interview for CNN, Anna Coren asked him, "There is a real sexualization, some would say exploitation, of teenage girls in Japanese society. And, in your videos, you do have young girls — either they're dressed in their school uniforms, or in bikinis, sexy lingerie, licking food off each other's faces, kissing, bathing. Are you, in some way, contributing to the problem?"

Akimoto replied, "No. It's an expression of art."

He has avoided the foreign press since.

This year, Lighthouse, an organization that supports victims of human trafficking, published Blue Heart, a comic aimed at teen girls warning them about the perils of the JK business.

"The JK Business is a blight on Japanese society," Lighthouse founder Shihoko Fujiwara tells VICE News. "I can't say that the existence of AKB48 encourages it, but we hear the name a lot. This is how girls are tricked into doing porn — 'So-and-So of AKB48 now does adult video (AV). It's one way to become a star.'"

She says it's not unusual for young girls to be offered a contract that "will make them a teenage idol." They're scouted on the streets and taken to a "modeling agency." They sign a contract and are immediately told they're going to be an AV star. The scouts knowingly recruit underage girls to appear in porn, but only the scouts themselves are held responsible — the producers pretend not to know that the girls are underage. The scouts are well-paid for taking the risk, though prosecutions are very rare.

"Japan has a culture where sex is something to be merchandised and sold," Fujiwara says. "Many people don't see that as a problem — neither women nor men. But when young women and girls are tricked, deceived, and exploited in that business, it's a human rights problem."