He attended the Second Vatican Council from 1962 to 1965, and was promoted to the rank of metropolitan archbishop on July 24, 1969. He also served as President of the Japanese Episcopal Conference from 1970 to 1978.
On November 25, 1941, Taguchi was appointed Bishop of Osaka by Pope Pius XII. He received his episcopal consecration on the following December 14 from Apostolic Delegate in Japan Archbishop Paolo Marella, with Archbishop Peter Doi and Bishop Johannes Ross, S.J.