At around 7:20 p.m., officers entered the residence, located in Wakamatsucho, and found Tomomi Hayakawa, 33, dead atop a futon inside a room with markings consistent with strangulation on her neck.
As well, the 38-year-old male resident of the apartment was found collapsed and unconscious inside another room. He was rushed to a hospital where he remains unconscious, according to the Sano Police Station.
The residence had been sealed with weather stripping. As well, a saucepan with burned charcoal briquettes was found on a table. It is suspected that the man collapsed after suffering from carbon monoxide poisoning, police said.
The cause of death of Hayakawa, who was employed at a association and lived in the same city, was later revealed to have been suffocation, police said.
Earlier on Tuesday, the boss of the man visited a police box to report that he had not arrived at work. The day before, the family of Hayakawa reported her missing with police.
Police are treating the case as murder-suicide.
