A family of four was found stabbed to death Sunday morning at home in Tokyo's Setagaya Ward, police said.
The victims were identified as Mikio Miyazawa, the 44-year-old operator of a cram school in Kami-Soshigaya, Setagaya Ward, his 41-year-old wife Yasuko, their 8-year-old daughter Nina and 6-year-old son Rei.
The father was found on the ground floor and the mother and two children were in a room on the second floor, police said, adding that they had stab wounds in their necks and elsewhere.
Later Sunday, police said two kitchen knives covered with blood were found on the second floor.
The four victims were wearing casual clothes, police said. Police believe they were slain sometime after Saturday afternoon because a neighbor met Miyazawa around noon that day.
The inside of the house was messy, although the main entrance was locked and no windows had been broken, they said.
The Seijo Police Station of the Metropolitan Police Department has set up an investigative headquarters for the case, suspecting the four were killed during a burglary attempt.
Yasuko's 71-year-old mother, who lives next door with Yasuko's elder sister's family, found the bodies when she entered the home using a duplicate key after repeated phone calls to their house went unanswered, police said.
Miyazawa operated a cram school on the first floor of the home and used the second floor as living quarters.
The house is located in a quiet, affluent residential area surrounded by the Tokyo Metropolitan Soshigaya Park and the grounds of Komazawa University.