Torrential rains kept pounding Japan following the passing Wednesday of Typhoon Etau.
At one point in Sendai, capital of Miyagi, more than 410,000 people were advised to evacuate.
In Joso, which is located in the Ibaraki Prefecture about 50 kilometers north of Tokyo, hundreds of people were left stranded overnight awaiting rescue after the Kinugawa River burst its banks.
The river banks were breached for the first time in 66 years.
Many houses are believed to have been inundated.
On Friday, the Metropolitan Police Department plans to send 100 officers from its riot police and other forces to Joso.
The Tokyo Fire Department also sent a rescue team with helicopters.