Okamoto guided Japanese and American diplomatic relations throughout the 1980s, during an era when both countries simultaneously competed for economic influence on the global stage.

He was posted to diplomatic missions in Paris, Cairo and Washington D.C.[1] Okamoto rose to become the director of the foreign ministry's First North America Division, which guided U.S.-Japanese relations.

He closely advised Japanese prime ministers on some of their most sensitive bilateral issues, ranging from the controversial U.S. military bases on Okinawa to the commemorations marking the 70th anniversary of World War II in 2015.

[2] Okamoto was appointed to an advisory panel which helped draft Prime Minister Shinzo Abe's speech marking the 70th anniversary of the end of World War II in 2015.

[2] Okamoto, who was fluent in English, continued to lobby for close American and Japanese bilateral relations, as well as Japan's foreign policy positions on the world stage.