Recently, an unsettling case that once shook Japan has reached its conclusion. The Wakayama District Court ruled that 28-year-old suspect Sato Sayaka, who was accused of murdering her 77-year-old husband, Nozaki Kōsuke, in May 2018, has been acquitted due to insufficient evidence. Nozaki’s murder charge was dropped, and Sato was set free!
A Shocking Decision
The news sent shockwaves through Japan’s media and social platforms. Sato Sayaka, who was the primary suspect, raised numerous doubts, but the lack of direct evidence led to her acquittal. Some have called it a “perfect crime.”
The story of this perplexing case begins with Nozaki Kōsuke, a man who fancied himself as Japan’s very own “Don Juan“—a notorious playboy. 
The Rise of Nozaki Kōsuke
Nozaki Kōsuke, born in 1941, came from a poor family in Wakayama Prefecture, an area once known as “Kishu.” Despite his humble beginnings, he would rise to fame as a successful businessman, accumulating wealth through various ventures, including selling contraceptives. Ironically, it was his success in selling these products that shaped his notorious reputation. Nozaki not only profited from his sales but also became embroiled in numerous scandals, breaking up many families in the process.
His business acumen and knack for making money gave him the freedom to indulge in his passions—women. Nozaki was known for his promiscuity and was open about his relationships with over 4,000 women. He even published a book in 2016, titled The Don Juan of Kishu, bragging about his romantic conquests.
Enter Sato Sayaka
Sato Sayaka, a young woman in her twenties, seemed like a perfect match for the aging playboy. She had a history of scamming men for money and had possibly been involved in a sugar daddy relationship before meeting Nozaki. She came from humble beginnings but found herself at the heart of Tokyo’s glamorous nightlife scene. At the time, she was known for her fondness for luxury brands and had an affinity for wealthy older men.
The two met in 2017 at Haneda Airport when Nozaki nearly stumbled while walking, only to be caught by Sato. This encounter would set the stage for their whirlwind romance. Nozaki, in his mid-seventies, was enamored with Sato, and within months, they were married. She, in turn, promised him she would fulfill his every desire as long as he met her material needs.
In February 2018, Nozaki, 55 years her senior, married Sato Sayaka, and soon after, their relationship took a strange turn.
The Strange Marriage
After their marriage, things did not go as expected. Sato grew cold toward her husband. She refused to share a bed with him most nights and would only allow him to sleep beside her if he wore rubber gloves. Nozaki, once a confident playboy, found himself frustrated by her indifference.
But that wasn’t the only problem. Sato continued to spend excessively, visiting hostess clubs and indulging in lavish shopping sprees. Despite her new husband’s wealth, she showed little regard for his feelings.
Things got even stranger when Nozaki began experiencing health issues. Just two months after the wedding, he suffered two strokes. In May 2018, his long-time pet dog also mysteriously passed away, which added to Nozaki’s unease.
The Mysterious Death of Nozaki Kōsuke
On the evening of May 24, 2018, Nozaki was found dead in his bedroom. Sato Sayaka was the first to discover his body and quickly alerted the maid. After a discussion, they called the police. Authorities soon launched an investigation.
The preliminary cause of death was determined to be “acute stimulant poisoning.” Nozaki’s body contained a dangerously high level of stimulants, far beyond what a normal person could tolerate. The authorities found no injection marks on his body, and his hair showed no traces of the stimulant, which led them to suspect that he had ingested it orally.
Was It an Accident or Murder?
The question remained: Did Nozaki die from an accidental overdose, or had someone deliberately poisoned him? Investigators began to dig deeper.
They tested several empty beer bottles and the dead dog’s body but found no traces of stimulants. They also ruled out suicide. The conclusion they arrived at was chilling: someone had likely forced or tricked Nozaki into consuming the deadly stimulant. The prime suspect? Sato Sayaka.
The Investigation into Sato Sayaka
Over the next few years, police conducted an in-depth investigation into Sato’s involvement with stimulants. They discovered that she had searched for terms like “stimulants,” “death,” “elderly,” and “perfect crime” on the internet. Further investigation revealed that she had made contact with people who sold stimulants online.
In April 2021, the police arrested Sato Sayaka. She was charged with murder and violating Japan’s Stimulant Control Law.
The Legal Battle
What followed was a long and tumultuous legal battle. Despite the evidence suggesting Sato’s involvement with stimulants, her lawyer argued that there was no proof she directly caused Nozaki’s death. Sato herself claimed that Nozaki had asked her to buy stimulants for him, and she did so reluctantly. She also argued that she had no motive to kill him, given the money he had been providing her.
The prosecutor’s case was built around the idea that Sato stood to inherit a large sum of money after Nozaki’s death. Nozaki had written a will stating that his fortune—valued at 13.2 billion yen—was to be donated to his hometown. However, under Japanese law, Sato would still be entitled to half of that fortune, a sum of 6.6 billion yen.
Despite the compelling circumstantial evidence, the court concluded that there was no definitive proof that Sato had forced Nozaki to ingest the stimulant.
A Perfect Crime?
On December 12, 2021, the Wakayama District Court ruled that there was insufficient evidence to convict Sato Sayaka. She was released, and the six-year-long “Kishu Don Juan Death Case” came to an end.
Was this truly a case of “perfect murder,” or just an unfortunate accident? Only time will tell, and the mystery surrounding Nozaki’s death is likely to remain unsolved for many years to come.
