In 2010, while covering the issue of the “secret agreement” at the Ministry of Foreign Affairs, the author came across diplomatic documents relating to the reversion of Okinawa and was particularly impressed by the handwritten documents of Kazuo Chiba, then Director of the North American First Division at the Ministry of Foreign Affairs, which, unlike ordinary bureaucrats, “stood out from the crowd and seemed unique”. The name of Chiba subsequently appeared in a number of documents left by former Prime Minister Eisaku Sato’s secretary, and the author became interested in finding out what kind of person he was.