An internal report by Japan's Self-Defense Forces shows that ground troops sent to South Sudan were caught in crossfire, even though they were only supposed to operate in non-combat zones.
NHK obtained a copy of the report through the information disclosure system. It was compiled by the engineering unit that was engaged in peacekeeping operations when a major armed clash occurred in July 2016.
Some parts of the report were blacked out, but NHK discovered the contents through investigative reporting.
During the clash, South Sudan's government and opposition forces were located on the northern and southern sides of the SDF camp in the capital, Juba, and exchanged fire.
The report says SDF personnel were forced to take cover in containers twice during the gunfight.
After the situation calmed down, 25 bullets and 9 bullet marks were found at various locations in the camp, including the living quarters.
The report says the SDF personnel found side wall damage from direct gunfire at 3 locations, in addition to roof damage caused by stray bullets.
The SDF held a debriefing for those who were in charge of security at that time to assess the psychological impact of the incident.
Some personnel were isolated and felt deep fear during the fighting, while others were visibly irritated or had difficulty sleeping after the incident.
The Japanese government said the incident did not breach the country's criteria for peacekeeping missions, which includes a ceasefire agreement between conflicting parties.
Five months after the clash, the government allowed the unit to expand the use of force to defend UN peacekeepers and aid workers. The SDF mission ended in May last year.
Sophia University Professor Daisaku Higashi says the government should disclose information to help the public discuss the best ways for the SDF to carry out its overseas missions.
He says the report shows there were high security risks in South Sudan, and the SDF's experiences and the lessons learned will be an asset for future missions. Higashi also stresses the need to keep the public fully informed about the SDF's activities.