Osaka police have arrested a man suspected in the poisoning death of a university student in Kyoto in October last year and sent him to prosecutors on Saturday for the alleged murder.

The police allege that Kazuki Miyamoto, 37, killed Hinako Hamano, a 21-year-old student of Ritsumeikan University, by getting her to ingest a lethal amount of thallium, a highly toxic substance that was once widely used as rat poison.

Miyamoto has refused to speak since his arrest Friday, but before that, he voluntarily answered questions, telling police that when the two were together at her home in the city, he had "bought some medicine at a drugstore and gave it to her as she wasn't feeling well," according to an investigative source.

The man, who is in the real estate rental business, and the woman had met through her part-time job, according to investigative sources.

On Oct. 11, the two dined out in Kyoto before going to Hamano's home to drink. Once there, her health suddenly deteriorated, and she began having severe fits of coughing, Miyamoto was quoted as telling investigators earlier.

The suspect contacted her family, who took her to a hospital in Osaka Prefecture the next day. However, her condition worsened, and she died on Oct. 15.

A doctor at the hospital where Hamano had been transferred prior to her death notified police of suspected foul play, according to police.

Her autopsy indicated her cause of death was acute respiratory distress syndrome, which prevents the lungs from providing vital organs with sufficient oxygen, due to thallium poisoning.

Symptoms include severe shortness of breath, low blood pressure, and confusion.

Traces of the toxic substance were found in her vomit and urine. Based on security camera footage obtained during their investigation and the opinions of toxicologists, police determined that Miyamoto got the woman to ingest the substance while they were alone at her home.

Hamano, a third-year student at the private university, is not believed to have been suicidal, with her parents telling the authorities that she had various plans for the future, the prefectural police said.

They are investigating how Miyamoto may have gotten Hamano to ingest the substance, including the possibility that he may have mixed it with a drink.

They also want to determine how he may have procured the legally restricted substance. Under the law, substances that include sulfuric thallium cannot be sold to those under 18 years old. Buyers are mandated to record their name, job, and address with the sellers.

Besides his real estate-related business, Miyamoto runs another company that provides maiko entertainment shows for tourists and is regarded by his acquaintances as a successful businessman. Geisha apprentices are known as maiko.

A hotel manager who had spoken with him several years ago about entertainment shows said Miyamoto had told him that he returned to Kyoto from Tokyo and was doing maiko-related business because he was fond of them.

The last high-profile arrest that involved thallium poisoning was of a Nagoya University female student in 2015. She was convicted of attempting to murder two classmates as a high school student in 2012. She said she lied about her age when she procured the substance from a drugstore.

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