Two bodies were found in a home in Morioka, Iwate Prefecture, where a fire broke out on Wednesday morning, the police said. They believe one of the individuals was murdered.
Two other fires broke out in the area, including at a house where a relative of one of the victims was thought to live.
Police identified one of the victims in the first blaze as Mitsuo Yoshida, 65 years old and unemployed. His body was found in the yard with injuries to the head and face consistent with being punched. A second body, believed to be a male, was found indoors on the first floor.
Investigators are treating it as a possible case of murder and arson.
A second building blaze and a car fire also occurred in the area, and police are examining a connection. They suspect arson in all three cases.
The second fire burned down four houses. There are unconfirmed reports that the building where the blaze began belonged to a relative of Yoshida, a 60-year-old man whose whereabouts were unknown.
Neighbors had seen a white car parked in front of Yoshida's house since Tuesday night. The man whose whereabouts are unknown also drives a white car.
Police said Yoshida was living there with his wife and that she witnessed an argument between him and another man. Other witness accounts say Yoshida may have gone into the house with the man.
A 40-year-old woman who lives next door said she heard the sound of breaking glass and Yoshida shouting at the time when the fire broke out, around 3:30 a.m.
"I thought someone had gotten very drunk. But the atmosphere was tense and I became scared," she said.
The home is located about 7 km from the city center in a quiet residential area.