Rikken Minseitō
In 1928, Katsu was elected in the Japanese general election of 1928 to the lower house of the Diet of Japan, under the Rikken Minseitō party. He was reelected six times to the same seat. In 1928, he was appointed Parliamentary Under-Secretary for Finance under the Hamaguchi administration and Vice-Minister for Commerce and Industry under the Okada administration in 1934. In January 1940, he was appointed Communications Minister in the Yonai administration