Photo/Illutration Kazuki Miyamoto on his Facebook page (Taken from Kazuki Miyamoto’s Facebook page)

OSAKA—Police here arrested a property-rental manager on suspicion of murdering a female acquaintance by slipping a highly lethal dose of thallium into her beverage during a drinking session.

The suspect, Kazuki Miyamoto, a 37-year-old resident of Kyoto, has refused to talk about the case to police since his arrest on March 3, investigative sources said.

Hinako Hamano, a 21-year-old junior at Ritsumeikan University in Kyoto, died under mysterious circumstances in October last year.

After becoming ill while in the company of Miyamoto, Hamano was taken to a hospital in Osaka Prefecture, where she was originally from.

Her condition worsened, so she was transferred to a general hospital. She died three days later, on Oct. 15.

A doctor at the general hospital called police on the afternoon of Oct. 12, suggesting a criminal act may have caused Hamano’s grave condition.

A forensic autopsy determined the cause of death was severe respiratory failure. Police also found thallium in the student’s vomit and urine.

According to the investigative sources, Hamano had consumed far more than 1 gram of thallium, the lethal dose for an adult.

Thallium is a highly restricted heavy metal that can be used in high-tech electronics and medical equipment. It is said to be a preferred weapon of assassins because it is so difficult to detect.

Osaka prefectural police focused on what the student was doing on Oct. 11 and 12, before she was taken to the hospital.

They learned that Hamano had met Miyamoto through her part-time job, and she also worked at an event organized by Miyamoto’s company.

Miyamoto grew up in a “wealthy family” in Kyoto, according to the sources.

He worked for a major company in Tokyo before returning to his hometown of Kyoto and managing the property rental business. He also organized events featuring “maiko” apprentice geisha.

According to acquaintances, Miyamoto and Hamano sometimes wined and dined together, and they appeared happy in each other’s company.

Prefectural police said Miyamoto and Hamano dined at two places on Oct. 11, including a bar in Kyoto, before going to Hamano’s home, where they continued to drink alcohol.

The student’s health condition abruptly changed.

Before his arrest, Miyamoto told police, “Hamano suddenly started coughing.”

He said Hamano had told him not to call for an ambulance because the coughing was only an “asthma attack.”

The next morning, when the student’s coughing continued, Miyamoto called her mother.

He said he didn’t take her to a hospital because “I had work to do and I asked her parents (to take care of her),” the sources said.

According to the sources, however, police confirmed that Miyamoto went to a golf driving range during the daytime on Oct. 12.

His suspicious words and actions made him the target of the murder investigation, the sources said.

Police suspect Miyamoto could have made Hamano drink alcohol mixed with thallium when they were alone on Oct. 12.

But how he could have gotten his hands on thallium is a mystery. Police also have not determined a motive.

Thallium has no taste or smell, making it difficult to detect if it is mixed in a drink in a powdery form, according to Kazuma Higashisaka, associate professor of toxicology at the Graduate School and School of Pharmaceutical Sciences of Osaka University.

Thallium consumption causes symptoms such as vomiting, stomachaches and potentially deadly breathing difficulties, he said. 

“Consuming thallium can cause coughing,” Higashisaka said. “If you consume a large amount, it expedites the start of coughing.”

There are strict rules on obtaining thallium in Japan.

In most cases in Japan, researchers or companies buy the substance from specialist businesses.

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