Mermet-Cachon was born in
La Pesse, in the
Jura department in
Franche-Comté in eastern France. He entered the seminary of the
Paris Foreign Missions Society in July 1952 and was ordained on 11 June 1854. On 25 August 1854, less than two months after his ordination, he was sent to
Hong Kong. Together with Father Prudence Seraphin-Barthelemy Girard and Father Louis-Theodore Furet, he arrived at
Naha, the capital of the
Kingdom of Ryukyu on 6 May 1855. During his two years in Okinawa, he was unable to win a single convert; however, during this time he developed a working knowledge of the
Japanese language. On his return to Hong Kong, he was recruited by
Jean-Baptiste Louis Gros, whom he assisted at
Edo with the negotiations cumulating in the
Treaty of Amity and Commerce between France and Japan which was signed on 9 October 1858. In November 1859 he returned to Japan, this time to
Hakodate, the main town on the island of
Hokkaido where he opened a French-language school of French in April 1860; however, his efforts to open a hospital were frustrated as
Russian Orthodox missionaries had arrived first, and had received official blessing to establish a clinic. His efforts as a missionary also met with no success, and disappointed and humiliated, and suffering from ill health, he left Hakodate in 1863. Mermet-Cachon returned to Edo and served as an interpreter for Prince
Gustave Duchesne de Bellecourt, who was a strong advocate of the use of force to govern relations with Japan and who supported the French intervention in the 20 July 1863
Bombardment of Shimonoseki. After returning to France in July 1863, Mermet-Cachon abandoned the Paris Foreign Missions Society, and after renouncing his vows as a Catholic priest, returned to Japan in a private capacity as interpreter to the French diplomat
Léon Roches in April 1864. On 1 April 1865, he established a French language school in
Yokohama and took a former prostitute as his common-law wife. He returned to France again on 27 October 1866, apparently with the intention of making only a short stay; however, in 1867, he was requested to serve as an assistant to
Tokugawa Akitake, the 14-year-old son of
Tokugawa Nariaki,
daimyō of
Mito Domain, who had arrived as a special envoy of the
Tokugawa shogunate for the
1867 World Fair in
Paris, where Japan had a pavilion. He also acted as interpreter for Tokugawa Akitake's audience with
Napoleon III, which subsequently resulted in strong French support for the Tokugawa shogunate. Mermet-Cachon never returned to Japan, but died in
Cannes on 14 March 1889. His grave is at the
Père Lachaise Cemetery in
Paris. ==See also==