Revealed: The gruesome true story behind international bestselling Japanese novel Butter

Readers around the world are finding themselves utterly captivated by a dark murder mystery set in Japan - Butter, by Asako Yuzuki. The crime thriller originally came out in Japan back in 2017, where it became an instant bestseller, before it was published in the UK in February last year. The novel, which follows the extreme lengths a female reporter goes to secure an exclusive interview with a suspected serial killer with a taste for fine dining, is based on a true story - that of convicted serial killer Kanae Kijima.

She is also known The Konkatsu Killer, as she frequently used marriage-hunting websites - konkatsu in Japanese - to find prospective partners. Another moniker used was the Lonely Hearts Killer. It's reported that she initially connected with the three men who would later become her murder victims on dating sites, before meeting them in person in the Tokyo area. Born in 1946 in Kitakyushu city, Fukuoka, Kijima grew up in a middle-class family, and earning good grades at school, she dreamt of going to university.

However, her very traditional father, who worked in a steel factory, did not believe women should pursue higher education. Instead, she gained employment as a bank teller, working there for four years between 1965 and 1969, until she married her first husband, with whom she had two children. She is now a mother of five. Kanae Kijima, also known as the The Konkatsu Killer, was found guilty of murdering three men and sentenced to death (picture date unknown).

Originally a truck driver, her husband had become a successful entrepreneur, building a fabric printing company. He died aged just 54, in 1994, after being discharged from hospital following a heart attack. Under Kijima's management, his previously successful business went under in 2003. Her second husband, who she wed just a year later, was a manager at a pharmaceutical wholesaler. He died aged 69 in 2006 from a stroke.

Two years later, she married again. Her 75-year-old husband, who ran an agricultural cooperative, died just three months later from a heart attack. Some are now suspicious about these deaths, but as the bodies were cremated, any forensic examination is impossible. The three victims she was found guilty of murdering are Takao Terada, 53, Kenzo Ando, 80, and Yoshiyuki Oide, 41. It's believed she dated the three men for their money, turning on the charm and using her culinary skills to lure them in, before killing them within an eight month period in 2009.

Kijima's first of these three victims, 53-year-old Takao Terada was found dead in Tokyo in January 2009. The Supreme Court rejected Kanae Kijima's final appeal in 2017, meaning she will face execution. Kenzo Ando, 80, died in his home in Chiba prefecture in May 2009, and three months later 41-year-old Yoshiyuki Oide was found poisoned in a rented car, also from briquette fumes. Kijima, who killed the men through carbon monoxide poisoning by burning charcoal briquettes after giving them sleeping tablets, claimed she was innocent.

Her legal team argued that all evidence against her was circumstantial, and that the men had died by suicide. And indeed, when Yoshiyuki Oide's body was found by police in his rental car, they initially believed he had died by suicide. However, they were confused to discover there were no keys in the ignition. In addition, Mr Oide appeared to be happy and looking forward to the future. According to reports, less than 24 hours before his death, he wrote on his blog: 'At 41, I’m actually looking forward to getting married, and today I’ll meet my partner’s family.

'Recently, we’ve spent all our time looking for a new place to live and talking about our new life together. This evening we’re going on a two-night, three-day holiday.'. On top of that, not long before he passed away, he had transferred five million yen (around £26,000) to his fiancee's bank account. Waterstone's Book of the Year Butter by Asako Yuzuki is based on the real-life story of Kanae Kijima.

When a postmortem was carried out, the cause of death was determined to be carbon monoxide poisoning, however traces of sleeping pills were found in his blood. When it came to another of the killings, a report in Japanese media claimed that Kijima was filmed withdrawing money using a cash card belonging to one of her victims, Kenzo Ando, the same day he died in a house fire. Kijima worked as a home help for Mr Ando, and had visited his house the day he died. A postmortem also found sleeping pills in his blood.

Her defence did not convince, and the prosecutor's argument that she had squeezed money from the men, then killed them so she wouldn't have to pay them back led to her conviction. According to some reports, between between loans, inheritance, and life insurance payouts, Kijima pocketed some one billion yen (around £5 million), which she largely squandered on poor investments. Kijima was convicted without the witness testimony or confession often relied upon in Japanese prosecutions.