In 1982, the Edo Shoji Corporation is a large Japanese trading company that has created a new branch in the fictional country of Cannibalia (or Kanivaria depending on how you transcribe it).
Having joined the workforce after his days of being a sumo wrestler, Hitoshi finds himself rapidly climbing the corporate ladder.
Hitoshi finds himself assigned to the city of Esecarta in the Republic of Santalna, a South American country that is in a state of political turmoil.
However, while reading some information at the Japanese embassy, Hitoshi learns of a certain metal that is indispensable to the manufacturing of electronics.
The page for Gringo at TezukaOsamu@World claims that the protagonist was based on Nobuyuki Wakaoji, a Japanese businessman who was kidnapped in the Philippines in 1986 and released after four months of captivity.