[5] Using his diplomatic passport that allowed him great freedom of movement, Shimoi acted after the war as a liaison for messages between Gabriele D'Annunzio, then regent of Fiume, and Benito Mussolini, at the time the head of the Italian Fasci di Combattimento and editor of Il Popolo d'Italia .

Returning to Naples in 1920, he founded the Japanese literature magazine Sakura, that would be published until March of the following year for a total of five issues.

Getting back to his homeland, Shimoi helped the Italian Embassy in Tokyo to stop the pro-Ethiopian activities of the Japanese rightist clubs during the war in Ethiopia.

He argued that fascism was a natural ramification of the risorgimento, and that its role was to be a "spiritual movement" that would make Italians identify as being part of the new nation.

[6] After the second World War, Shimoi met and became friends with Indro Montanelli, who arrived in Japan to work on a series of reportages.

Some of his works include Shito Ponpei o otonau tame ni (死都ポンペイを訪ふために, "To visit the ghost town of Pompeii") (1926) and La guerra italiana vista da un giapponese ("The Italian war as seen by a Japanese") (1919).