From the wiki: “On December 22, 1885 the Ministry of Communications was established, combining the Bureau of Posts and Post Station Maintenance and Shipping Bureau formerly under the Ministry of Agriculture and Commerce with the Telegraph Bureau and Lighthouse Management Bureau formerly under the Ministry of Industry.
“On August 16, 1891, the ministry was also placed in charge of the nascent Japanese electric power industry. On July 21, 1892, the Railway Bureau was transferred to the Ministry of Communications from the Home Ministry and from November 10, 1893, the ministry was charged with the supervision of all land and water transportation businesses. (However, on December 5, 1908, the Railway Bureau was separated to become an independent bureau reporting directly to the Cabinet.)
“In April 1923, responsibility for civil aviation supervision was transferred to the Ministry of Communications from the Army Ministry.”