Photo/Illutration Kenichi Hosoya and his wife, Shiho, are suspected of murdering two people by poisoning. (Asahi Shimbun file photos)

A Tokyo couple accused of fatally poisoning their 4-year-old daughter were rearrested on March 6 on suspicion of murdering the girl’s aunt with the same toxic substance.

The suspects, Kenichi Hosoya, 43, and his wife, Shiho, 37, have declined to comment on the allegations, investigative sources said.

Kenichi’s older sister, Minako Hosoya, a 41-year-old printing company employee, was found dead in her apartment in April 2018 after she failed to come to work for two days, the sources said.

An administrative autopsy found no cause to suspect foul play.

But Minako had no apparent reason to commit suicide. And investigators examined a preserved sample of her kidney following the suspicious death of Yoshiki Hosoya, the couple’s second daughter, in March 2023.

The study of the kidney found calcium oxalate, a substance generated when ethylene glycol, which is often used as antifreeze, is taken in, according to the Metropolitan Police Department.

Records show that Minako saw a doctor and complained about a headache a few days before her death, the sources said.

The couple, who were living in the same apartment complex as Minako, had a duplicate key to her housing unit, the sources said.

Police concluded that the couple were the only people who could have gotten Minako to ingest ethylene glycol, which is primarily used for industrial purposes, the sources said.

Kenichi succeeded his father as head of a hotel management company after his death in June 2018. Shiho became a director of the company the following month.

Minako, who was helping with the company’s accounting on weekends, was opposed to Kenichi taking over the operations because of his spending habits, according to sources.

Kenichi reportedly told an aquaintance after Minako’s death that she had never trusted him with finances and that he had been unable to freely spend money.

A judicial autopsy of Yoshiki’s body detected substances that result from the consumption of ethylene glycol and olanzapine, an antipsychotic drug.

The girl, who had shown signs of abuse and neglect, had no medical reason to take olanzapine.

Police arrested the couple on Feb. 14 on suspicion of murdering the girl at their apartment in Tokyo’s Taito Ward by poisoning her with the two substances.

Police sources said either Kenichi or Shiho bought ethylene glycol online a few days before the deaths of both Minako and Yoshiki.

During police questioning about Minako’s death, Kenichi said he “cannot talk now” and Shiho has remained silent, the sources said.

(This article was written by Minami Endo and Yuji Masuyama.)

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