Maximum sustained winds of around 55 mph near the storm’s center were accompanied by heavy downpours that triggered flash flooding.
Two of the victims were hikers who drowned as they crossed a swollen stream in an area where 5 inches of rain fell within three hours.
Other victims were a taxi driver who became stranded in flood waters and a TV reporter who fell into the sea while reporting on the storm from a pier.
Dianmu had earlier drenched coastal parts of China’s Shandong province with downpours that forced the evacuation of 158,000 residents, according to China’s Ministry of Civil Affairs.
The storm later brought heavy rains to parts of northern Japan before dissipating over the North Pacific.
Dianmu is the name of the goddess who commands thunder and lightning in Chinese mythology.
Tropical Storm Dianmu Track
Radar Loop Data: Korea Meteorological Administration