Katō Hiroharu was born in Fukui City in Fukui on 2 November in the 3rd year of MeijiOn Japanese Lunisolar calendar then in use. (23 December 1870) as the eldest son of one of the first navy officers, Katō Naokata, of Fukui Domain in Imperial Japan before the Abolition of the han system. On 17 July 1891, he graduated top of the class from Imperial Japanese Naval Academy, 18th class. He was assigned to cruiser Naniwa as a cadet as of 20 May 1892 and experienced two tours to Kingdom of Hawaii. While at Honolulu on the second tour, he was promoted to ensign on 1 March 1894. He was assigned as a navigator on cruiser Hashidate.
