Police in Japan have arrested two more people in a case in which the burned bodies of a couple were found in the mountains in Tochigi Prefecture, north of Tokyo. One of the suspects is the common-law husband of the couple's eldest daughter.

Police believe the 32-year-old man, Sekine Seiha, masterminded the case. The bodies of Takarajima Ryutaro and his wife, Sachiko, were found in the town of Nasu in mid-April. Takarajima ran many restaurants in Tokyo's Ueno district. Sekine reportedly served as manager at Takarajima's firm.

Sekine was arrested on suspicion of damaging the corpses. Police also arrested Maeda Ryo, an executive of a real estate firm. He faces the same charge.

Maeda is said to have been acquainted with Takarajima and his wife. He is thought to have taken the couple to a vacant house, where they were allegedly attacked by two assailants.

Police earlier arrested four men, including a person who is said to have ordered the disposal of the bodies, a suspected middleman and the two alleged assailants.

According to investigators, the man who ordered the disposal said he was acting on a request by a certain individual. Police suspect that person is Sekine, the partner of Takarajima's daughter. Police are still trying to establish a motive for the crime.