According to the Japanese government, at least 155 people lost their lives in floods and landslides triggered by torrential rain in western Japan.
Rescuers are now digging through mud and wreckage in a race to find survivors, as dozens are still missing.
"I have asked my family to prepare for the worst," 38-year-old Kosuke Kiyohara, who has not heard from his sister and her two sons, told AFP.
Prime Minister Shinzo Abe has cancelled an overseas trip to deal with the flood crisis.
"We are checking every single house to see if there are people still trapped inside them. We know it's a race against time, we are trying as hard as we can," an official with the prefecture's government told AFP.