A 2-year-old boy died after his father forgot to drop him off at day care and left him in the car for more than eight hours in the Tochigi Prefecture town of Haga on Friday, when the mercury outside topped 30 degrees Celsius, police said.
According to investigators, the father, who is in his 30s, was supposed to take the boy to day care before heading to work at around 9 a.m. but "had forgotten" that his son was in the back seat.
When the mother came to pick him up at day care in the evening, she learned he wasn't there.
She hastily called her husband, who checked his car and saw his son unconscious in a child seat in the back, they said.
He was rushed to a hospital, where doctors pronounced him dead.
The toddler had what appears to be a burn on his body, police said, adding that he may have died from heat stroke. The police were to conduct an autopsy on Saturday.
The city of Mooka, next to Haga, registered 32.7 degrees C around 3 p.m. on Friday, according to a weather agency in Utsunomiya.