Chemical Linked to Death of Tokyo’s 4-yr-old Found in Body of Aunt; Father Bought Antifreeze Agent Around the Time of Death

The Yomiuri Shimbun
The apartment building where Yoshiki Hosoya was found dead in Taito Ward, Tokyo, is seen on Wednesday.

An antifreeze agent allegedly used by a couple to kill their 4-year-old daughter was found in the body of the girl’s aunt who died about six years ago, an investigative source has said.

Company executive Kenichi Hosoya, 43, and his wife, Shiho, 37, were arrested Wednesday on suspicion of killing their daughter Yoshiki last year in their apartment in Taito ward, Tokyo, by having her ingest ethylene glycol — an antifreeze agent often used in cars — among other substances.

The Metropolitan Police Department detected the chemical in the body of Kenichi’s older sister — then 41 — and also confirmed that Kenichi had purchased the agent around the time she died.

According to a police announcement, sometime around March 13 the couple allegedly poisoned Yoshiki by giving her olanzapine — a psychotropic drug — and ethylene glycol.

The investigative source said Kenichi’s sister was living in an apartment in the same residential building as the suspects and was found dead there in April 2018. The cause of death was not determined in the autopsy.

The MPD was investigating the circumstances of Yoshiki’s death, which led them to reinvestigate the circumstances of the aunt’s death. It analyzed a sample of her tissue that had been kept at a medical institute and detected ethylene glycol — a chemical also detected in Yoshiki’s body.

Analysis of the couple’s smartphones showed a history of purchasing antifreeze and olanzapine online on several occasions, starting about a year before Yoshiki died. The history also showed that they had purchased antifreeze online around the time of the aunt’s death.

Right: Kenichi Hosoya in August
Left: Shiho Hosoya in September

According to the Health, Labor and Welfare Ministry and elsewhere, ethylene glycol is a chemical substance used to prevent an automobile engine from freezing and is classified as a Category IV hazardous material, the same as kerosene, under the Fire Service Law. It can cause hyperventilation and kidney failure if ingested. It is colorless, clear, odorless, sweet-tasting and is said to give a warm sensation to the tongue when put in the mouth.

Kenichi took over operations of a hotel business in Tokyo’s Asakusa district from his deceased father in June 2018 and became the president. Shiho became a board director in August 2019 and was running the business together with Kenichi.

Yoshiki, who is the couple’s second daughter, was temporarily taken into protective custody in March 2019, when she was 2 months old. Even after returning to her parents, she had been left in a childcare facility for long periods and was suspected to have been routinely neglected. The MPD believe Yoshiki had been given psychotropic drugs for a period of time.

After the arrest, Kenichi denied the allegation, saying, “I’m not involved,” while Shiho remained silent, the police said.