In 1934, Hansgirg arrived in the Empire of Japanm where he worked with industrialist Shitagau Noguchi to set up a magnesium plant at the Chosen Nitrogen fertilizer complex in what is now the northern Korean city of Hungnam. Noguchi (through his company Nichitsu) and Winter (American Magnesium Metals corporation) established a subsidiary Japanese magnesium company. Hansgirg took the post of vice president of both American and Japanese magnesium companies, but there were problems with financing. Hansgirg's work was not limited to magnesium. In 1936, he founded a new firm Nitehiuu gemstones, because of the increased demand for jewel bearings for military purposes.
Hansgirg also developed a cracking plant, to break down crude oil into its various component parts. Before leaving Austria, he had designed two applications of a method of producing heavy water using a water gas shift reaction. It is thought that Hansgirg helped the Japanese to produce heavy water in Hungnam, and was suspected by the United States of aiding the Japanese nuclear weapon program.