A transgender man whose face had been cut off was found dead by his adopted son at their suburban home.
Mr Yoshi Tsuchida, 38, who the Sankei Shimbun appeared to have had his face “sliced off with a knife or another sharp instrument”, a police spokesman said.
Mr Tsuchida’s 28-year-old son – who has not been named – returned to the home they shared in west Tokyo early on Thursday morning, Jiji Press reported.
He fell asleep but later discovered his father, whose faceless head was covered with a plastic bag, the agency said.
“When I woke up my father was bleeding from the face,” Jiji reported him as saying, citing police sources.
It is believed that Mr Tsuchida adopted his son only recently – it is not uncommon in Japan for adults to be adopted.
Sankei said that his son was also trans and currently receiving female hormone treatment, however still identifies as male.
It added that there was a history of violence between the two men and that police officers had visited their apartment after receiving emergency calls reporting loud voices and people apparently fighting.
Tokyo police are yet to confirm the reports, but said Tsuchida was found wrapped in a blanket and was confirmed dead about two hours after his son made an emergency call.
Investigators were examining the case “on suspicion of damaging a dead body”, a Tokyo Metropolitan Police spokesman told AFP.
It is yet to be established if the murder was a hate crime or unrelated to the fact that the victim was trans.