Moriyama and 5 colleagues from his company in Wakayama Prefecture went to visit the Hidaka River in Hidakagawa Town on Sunday, Japanese media reported.
When the group entered the water to play games, two of them were swept away by the river’s strong current.
Moriyama used a surfboard to chase after them, but the board overturned and he could not stay above water.
One of the two colleagues managed to swim back to the shore, but Moriyama and the other employee, a 23-year-old Vietnamese, were swept away.
They were both found alive downstream later.
They pair were taken to the hospital, but Moriyama died. The Vietnamese employee is currently in critical condition.
An investigation is ongoing.