TOKYO (TR) – The Tokyo District Court has sentenced a 26-year-old woman to 12 years in prison for the fatal stabbing of her live-in boyfriend two years. The case shed light on a bizarre and cruel campaign of domestic abuse centered around his secret hair loss, reports the Sankei Shimbun (Nov. 28).
On November 21, 2025, Kotomi Sato was found guilty of injury resulting in death for plunging a pair of scissors into the neck of her 26-year-old boyfriend, Yuya Koya, an elite certified public accountant, inside his luxury high-rise apartment in Nakano Ward.
During the trial, prosecutors revealed a chilling dynamic of domestic violence in which Sato weaponized the victim’s deepest insecurity to keep him under her control.
The court heard that Sato, originally from Yamaguchi Prefecture, had quit her corporate job shortly after moving to Tokyo. She racked up heavy debts frequenting host clubs and eventually worked in the dispatch sex industry to fund her lifestyle. In January 2024, she met the wealthy accountant on a dating app, and the pair quickly began living together.
By April, the victim confessed to Sato that he suffered from severe alopecia and wore a wig to hide his condition.
Rather than offering support, Sato used the secret to ruthlessly dominate him. According to messages on the chat app Line presented in court, she would threaten to leave him over his appearance. She wrote, “You’re too bald. I want someone with hair after all.”
She routinely forced him into submission by threatening to expose photos of him without his wig on social media. Her control quickly escalated into physical violence, with the court hearing she beat him until his face swelled and strictly monitored his daily actions.
The fatal encounter unfolded on the evening of September 16, 2024. After a sushi date, the couple began arguing over a trivial matter. When the victim uncharacteristically stood his ground instead of immediately apologizing, Sato resorted to her usual blackmail.
“If you don’t fix your mood, I’ll post a picture of you without your wig on SNS,” she threatened, later adding, “I already posted it.”
After returning to the apartment, Sato armed herself with a pair of scissors featuring an 8-centimeter blade. She claimed during the trial that she only brought out the weapon “thinking he would calm down if he saw it,” and argued the fatal wound was a sheer accident that occurred during a 10-second struggle.
The Tokyo District Court dismissed her defense. Noting that the scissors penetrated 6 centimeters deep into the victim’s neck and that he lacked any defensive wounds on his body, the presiding judge ruled that Sato had forcefully swung the blade downward with a clear intent to assault.
In handing down the 12-year term, the court condemned the malicious nature of the crime and the psychological torment Sato inflicted on the victim by exploiting his physical vulnerabilities.
