The Mito District Court on Wednesday sentenced a 29-year-old man to 20 years in prison for killing his ex-girlfriend in December 2025. Prosecutors had been asking for a prison sentence of 21 years for Takumi Ouchi over the murder of nail artist Haruka Komatsumoto, then 31, in her apartment in Mito, Ibaraki Prefecture. According to indictment documents, Ouchi is accused of killing Komatsumoto on Dec. 31 by striking her head multiple times with a hammer and stabbing her neck with a knife.
He also loitered around her apartment for days starting on Dec. 28 and secretly installed a tracking tag on her car. The prosecutors said during the trial that Komatsumoto broke up with Ouchi in November 2024 but that he could not accept her decision. After she blocked his number, he started thinking about killing her so that he could return to the time before the two met and reset his life, according to the prosecutors.
They also said that the incident had been planned, as Ouchi had bought the hammer beforehand, and that it was brutal, with the victim having incurred injuries on at least 48 parts of her body. He purchased a Mickey Mouse plush toy, hid a tracking tag in it and sent it to her parents’ house five days before the murder, pretending that she won a lottery campaign. She took it to her apartment unit the following day, allowing him to identify where she lived.
Komatsumoto was married to another man at the time and was five months pregnant. Her husband, who married her six months before the murder, was the one to discover her following the attack. Her husband’s statement, read out during the first hearing of the trial, said the couple had been planning to report the stalking to police.
He asked for as harsh a punishment as possible, saying he lost his wife and their expected child all at once. His attorney asked for life imprisonment. The defense team argued during the trial that Ouchi had been aware of his abnormality and attempted to see a doctor, adding that he had been trying to hold back.
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