Two people were killed in separate fires in Gunma and Miyagi prefectures, one late Tuesday night and the other early Wednesday, police said.
The two-story wooden house of Torakichi Iwagami, 74, in Kiryu, Gunma Prefecture, burned down shortly before 1 a.m. Wednesday. Iwagami escaped alive, but police later found a charred body believed to be that of his eldest son, Etsuo, 51.
The cause of the fire was not immediately known. The son reportedly had trouble walking, and was temporarily back at home from a local hospital for the New Year's holidays.
In Sendai, a fire destroyed the house of Toshimitsu Sato, a 46-year-old self-employed worker, around 10:15 p.m. Tuesday.
After the fire was extinguished, a charred body believed to be that of Sato's wife, Yumiko, was found.
Sato suffered minor burns as he escaped from the fire, police said.
Meanwhile, in Niihama, Ehime Prefecture, an 18-year-old boy was arrested Tuesday on suspicion of setting fire to his family's home in an attempt to kill himself, police said.
The boy, identified only as a construction worker, allegedly destroyed the wooden house in the fire, which started shortly after 6 p.m. Tuesday.
The boy's father and elder brother, who lived together with the youth in the house, were away when the fire occurred.
The boy was found hiding at the home of a relative and arrested after admitting to arson during police questioning.