Photo: SPF
A Fatal Love Triangle
On Christmas night, 1969, Japanese mechanical engineer Hiroshi Watanabe decided it was time for his wife, Ayako, to meet his longtime mistress—Mimi Wong Weng Siu, a 31-year-old dance hostess in Singapore. Ayako, 33, had arrived just two days earlier with their three children, ready to start a new life with her husband.
That night, Mr. Watanabe drove his family to Wong’s house on Everitt Road. At first, Wong refused to meet Ayako, furious at the idea. But after Watanabe spoke with her privately for half an hour, she relented. The two families—Watanabe, his wife and children, Wong, her daughter from a previous relationship, and her servant—went out for dinner. Wong even gave sweets to Watanabe’s children.
Six days later, on New Year’s Eve, Wong attended a party at the Watanabes’ semi-detached house on Jalan Seaview. But behind the facade of civility, jealousy was brewing.
Consumed by Hatred
Wong was convinced that with Ayako now in Singapore, her affair with Watanabe was doomed. Her resentment turned into rage when Ayako allegedly called her a prostitute during the party.
On the night of January 6, 1970, Wong returned to the Watanabe home with her estranged husband, Sim Woh Kum, a 37-year-old sweeper struggling with financial troubles. Together, they brutally murdered Ayako Watanabe.
The killing was witnessed by nine-year-old Chieko Watanabe, Ayako’s eldest daughter. She would later become the prosecution’s star witness.
A Child’s Horrifying Testimony
Chieko recalled that her mother had tucked her and her siblings into bed that night while their father was working overtime. As she lay awake, she heard voices and footsteps downstairs. Moments later, she heard chilling screams from the bathroom.
“They were screams of pain from my mother,” she testified in court.
Rushing to the bathroom, she found her mother sitting on the floor, blood seeping from her chest.
“A man was pulling my mother’s left hand, and Obasan was pulling her right hand,” she said. “Obasan”—Japanese for “auntie”—was what her father had told her to call Wong.
Chieko cried out in horror. Wong quickly covered the child’s mouth with her hand. When Chieko stopped crying, Wong released her.
Ayako had suffered two fatal stab wounds—one to the neck and another that pierced her abdomen.
Chieko ran back to the bedroom and tried to wake her six-year-old brother, but he remained asleep. From the doorway, she watched as Wong and Sim fled down the stairs.
Meanwhile, her mother, bleeding profusely, staggered forward before collapsing.
“My mother stood in the bathroom. She staggered a few paces and fell. I thought she was dead.”
By the time Hiroshi Watanabe returned home, he was greeted by the heart-wrenching cries of his children.
He ran upstairs to find them standing outside the bloodstained bathroom. Inside, his wife lay in a crimson pool, still wearing her red dress from that evening.
Mr. Watanabe turned to his daughter.
“My father asked me who did it,” Chieko recalled. “I replied: ‘Obasan and a man whom I did not know.’”
The Murder Plot Unraveled
Sim Woh Kum confessed that Wong had approached him on January 2 with a plan to kill Ayako in exchange for money.
On January 6, they took a taxi to the Watanabe home. Wong carried a bag containing gloves and a knife, while Sim held a tin of toilet-cleaning liquid.
When Ayako answered the door, Wong told her she had brought a workman to fix a broken toilet basin.
Ayako let them in.
“I threw the liquid into the woman’s eyes,” Sim later confessed. “Wong stabbed her with a knife. The victim shouted—probably in pain—and covered her face with both palms while on the ground.”
As Ayako struggled, Sim tried to silence her by covering her mouth, but she bit his finger. This was when Chieko saw him.
“After stabbing her to death, Wong ran away. I chased her to the mouth of the road. We got a taxi…”
The next morning, police arrested Sim. Blood matching Ayako’s type was found on his trousers.
Blame and Betrayal
At trial, Wong denied planning the murder and instead blamed Sim. She claimed she had only wanted to slap Ayako for insulting her and provoke Watanabe into ending the affair.
She admitted drinking heavily that evening and bringing Sim along for protection, fearing that Ayako, like many Japanese, knew judo.
She claimed Sim attacked Ayako on his own.
“If I had not been drinking that day, this incident would never have arisen,” she told the court. “I am only a woman. I do not have the strength to stab her, especially when she was biting my left finger and grabbing my right hand.”
Sim, in turn, accused Wong of being manipulative and violent. He recounted how, during their failed marriage, she had abused his mother and frequently threatened him.
The Verdict and Execution
After a dramatic 26-day trial, both Wong and Sim were convicted of murder on December 7, 1970, and sentenced to death. Wong became the first woman in Singapore’s history to receive the death penalty.
Both showed no emotion as the sentence was read.
After exhausting all appeals—including one to Singapore’s President Benjamin Sheares—Wong and Sim were hanged at Changi Prison on July 27, 1973.
Fittingly, they were buried side by side.
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