Woman arrested with parents for beheading man in Japan hotel room

A headless body was found in a Sapporo hotel room three weeks ago.
Police arrested a woman, her father, and her mother in connection with the beheading.
The motive and relationship between the victim and suspects are still under investigation.
The victim's severed head was later found at the home of the arrested parents.
The woman is reported to have mental health issues and a reclusive past.