How the deaths of two girls, eight years apart, uncovered Tokyo’s worst predator.

Carita Ridgway loved to travel.

Perth-born, the 21-year-old found herself a quick way to fund her adventures after high-school: working in the lucrative hostessing industry in Tokyo.

It was sold to young western women as a 'safe' way to make a lot of cash, fast. And while it was considered on the fringes of the sex industry, sex wasn't actually required in this particular role — you just had to flirt, smile and pander to men in a club setting.

Listen: True Crime Conversations tells Carita's story. Post continues below.

Carita was beautiful, and had no trouble landing work. Her sister described her as a cross between Winona Ryder and Kate Moss, and someone that "men just melted" around.

Pretty quickly, Carita found herself inundated with offers for 'dohans' or 'dates-for-cash', a popular way for hostesses to make even more money. They'd attend romantic dinners and date customers outside the club, giving them more of a 'girlfriend' experience.

But even though it was an accepted 'extra', it was unsupervised and unchecked by the clubs.

On Valentine's Day 1992, on Carita's third and final trip to Japan, she unknowingly went on a dohan with a sadistic serial rapist.

She never made it home.

A mystery dohan date.

By Sunday, Carita hadn't returned from her Friday night date, and her sister was getting worried.

They were both staying at the same accommodation in Tokyo, but Samantha had been out with her boyfriend all weekend.

When she finally returned, another boarder told her a man had called and left a message.

Carita Ridgway died in 1992 in Tokyo aged 21. Image: The Sun.

"Your sister, Carita, has gone away with friends," he'd said.

Samantha knew it was odd. Who were these friends? Who was this man?

On Monday, she received a call from the local hospital, who told her Carita had been dropped off in the early hours of the morning with food poisoning from 'bad shellfish', and that she should come quickly.

Carita was unconscious, with the doctor diagnosing her with hepatitis and acute liver failure. She never woke up, and once her parents had also flown over to her bedside, the decision was made on March 2, 1992, to withdraw life support. Before her body was cremated, Carita's father requested that a sample of her liver be taken and saved. He couldn't have known this would prove crucial in the years to come.

Throughout the 17 days Carita was in hospital, the mystery man who'd alerted Samantha to her sister's hospitalisation regularly phoned her and her mother for updates, and even met with their parents briefly after Carita's death. Calling himself 'Akira', he told them, "I loved your daughter and I wanted to spend much more time with her," insisting that they accept a diamond necklace and ring he had planned to give Carita on her birthday.

It was all very odd, but despite the family's attempts, the local police weren't interested in investigating Carita's death. They made assumptions that she'd been on drugs and questioned her tourist visa, and why she was working on it.

"Sam was really offended," said author Clare Campbell, who spoke at length to Carita's family for her book, Tokyo Hostess: Inside the shocking world of Tokyo nightclub hostessing. 

"That whole week before Carita's death, [they] were trying to get the police to become interested, and they just didn't," she told True Crime Conversations.

In their grief, the family didn't push it and went home to Australia to mourn.

Eight years later: The disappearance of Lucie Blackman.

Lucie disappeared on July 1, 2000 in much the same circumstances as Carita.

She was a British 21-year-old working as a hostess in Tokyo, who never returned from a dohan date with a man named 'Akira'.

The mystery man had called Lucie's best friend, Louise, and told her that the former air hostess had joined a cult, and wouldn't be returning.

It immediately sent Lucie's loved ones into a panic.

Unlike Carita's case, Lucie made international headlines as her father and sister arrived in Tokyo and made sure the media knew about their missing loved one.

"It became an international news story thanks in part to Lucy's dad, who just went, 'Right, we've got to get this story out.' He knew how to work the media because the police weren't being cooperative at that point," Campbell explained.

After Lucie's disappearance, police discovered a serial rapist. Image: AAP/British Embassy.

Three months later, the horrible truth was uncovered when police arrested Joji Obara — a Korean-born real estate developer and businessman, who they discovered had allegedly raped as many as 400 women.

Detectives found videotapes of his crimes in his home, alongside multiple notebooks detailing his depraved interest in drugging, stripping and sexually assaulting unconscious women — many of whom were hostesses.

"He used to sort of prance about naked with this horrible mask on," Campbell told True Crime Conversations.

"And in the notebooks, he was saying that he wanted to have sex with 500 women by the time he was 50."

As police scoured Obara's notebooks, one scribbled note caught detectives' attention; "Carita Ridgway — too much chloroform."

They also found a tape detailing her sexual assault.

"On the tape of Carita, [police] wouldn't show the whole tape to her mother because obviously it would be too distressing," said Campbell.

Finally, Carita's family had the truth. She didn't die from food poisoning. The mystery man who left her at the hospital was Joji Obara, and she was one of his many victims.

Then, on February 8, 2001, Lucie's dismembered body was found in a sea-cave.

"It was horrible," Campbell told True Crime Conversations.

"They knew that he'd dismembered her body. They also found blonde hairs, which they matched with DNA from her family, [and] they found a photo negative that showed Lucy looking out to sea from the window in his apartment."

Watch: Lucie's story was turned into a Netflix documentary. Post continues below.

But they couldn't find a tape with Lucie on it, and as Campbell explained, "they had all this evidence, but they didn't have the tape… so they couldn't convict him of Lucie's murder, only that he'd dismembered her".

After a years-long court battle, Obara was convicted on April 24, 2007, of rape resulting in the death of Carita Ridgway. A police pathologist was able to use the liver sample that was saved to determine that consuming chloroform had led to her sickness and eventual death.

In December 2008, Obara was also convicted of abducting, drugging, and cutting up the body of Lucie Blackman. But not of her murder.

He was also convicted of raping eight others.

A courtroom sketch of Joji Obara who was arrested aged 48 after years of raping women. Image: AAP/Kyodo News, Tennen Katsuyama.

But hundreds of women visible on Obara's tapes and noted in his scribblings have never been found, and never come forward.

"It's changed totally today," said Campbell of the Tokyo hostessing and sex industry.

"Everything was cleaned up massively, and you have to have very strict rules about being a hostess. You can't go off and not say who you're with, they keep track of the men that are coming into the bars, and I also think the whole hostess industry has declined… people no longer thought it was safe," she told True Crime Conversations.

Obara, now 72, has never confessed, never shown remorse, and will likely never be released from prison.

While Lucie Blackman's name is synonymous with this case and this story, Carita Ridgway has often been referred to as the 'forgotten victim' because her case wasn't as highly publicised.

"I don't really know why; I suppose because with Lucie [the media coverage] started with 'where is she?' Whereas with Carita, she had supposedly died in hospital and the story just didn't get picked up.

"It's terrible that she should be forgotten in this way," said Campbell. "It was such a tragic story and she was such a lovely girl."

Feature image: The Sun/Ridgway family.