The male victim's body was found by a creek near the 2,728-metre Mount Hinokio in Nagano prefecture, a local police spokesman said.
Police found the bodies of three other South Koreans in the same area yesterday.
The four are believed to have died of hypothermia, Japanese media said, although police have yet to officially determine their cause of death.
They were part of a 20-member group of South Korean climbers, nine of whom went missing in bad weather. Five returned unharmed.