Japanese Emperor Akihito will visit Vietnam on a goodwill visit that will see him meet the abandoned wives of Japanese soldiers from WWII.
The emperor, whose role is symbolic in modern Japan, will also meet with Vietnamese President Tran Dai Trang this week and travel to Hue to visit the old Imperial Citadel, according to an itinerary provided by the Vietnamese Foreign Affairs Ministry.
Thursday's planned meeting between the Emperor and Empress and about 10 wives and children of Japanese soldiers, confirmed by the Japanese embassy in a statement, marks the most significant public acknowledgement of the issue from Japan.
By the end of WWII, hundreds of Japanese soldiers stayed behind to live with the Vietnamese wives they had married during their tours of duty. Estimates provided by the Japanese embassy put the number at 600 to 700 men.
Many went on to fight for the Viet Minh guerrillas, the predecessor to the Vietnamese communists who would defeat the US in the Vietnam War, against French colonialism.
The ones who weren't killed in Vietnam's independence war mostly returned to Japan in 1954. They weren't allowed to bring their Vietnamese families.
The two countries have fairly warm relations today, with Japan being the South-east Asia nation's largest provider of foreign aid. It is also the second-largest provider of foreign direct investment after South Korea.
Vietnam and Japan also share anxieties over China's maritime claims to the South and East China Seas respectively.
The imperial couple's trip follows a visit from Japanese Prime Minister Shinzo Abe to Hanoi in January, when he offered $US1 billion ($A1.3 billion) to help bolster Vietnam's maritime security.