The woman, whose identity has yet to be confirmed, was found with injuries to the neck and bleeding in the third floor apartment in a residential building in Hirano Ward at around 10:30 p.m. by another resident of the building, The Mainichi reported. An unidentified man, also believed to be Vietnamese, was found with similar injuries in another room.
A cooking knife with blood on it was found at the apartment entrance.
The woman was pronounced dead at the scene by the police, while the man was rushed to the hospital. His condition is now stable.
The deceased woman appeared to be one of three Vietnamese women living in the building, the police said.
They are investigating.
Last year a 9-year-old Vietnamese girl was murdered by a Japanese man in Chiba Prefecture in Tokyo. The murderer, Yasumasa Shibuya, 46, was sentenced to life last July.
The case sparked horror and outrage among millions of Vietnamese and Japanese at the time, with the girl’s bereaved parents launching a signature campaign seeking death for the killer.
Murder is punishable with death in Japan, with executions carried out by hanging. Death sentences are however rare and handed down only in cases considered particularly heinous.