Shirakawa and Kuwana
Koyama Munetsugu was born in 1803 (Kyōwa 3) in Shirakawa, in Mutsu province (today Shirakawa, in Fukushima). His elder brother, Koyama Munehira (固山宗平), was also a smith. According to the research by Maruyama Eiichi cited by the Japanese Wikipedia, in Shirakawa the Koyama were town smiths (町鍛冶, machi-kaji) and not in the service of the domain. In 1823 the Matsudaira, lords of Shirakawa, moved to the Kuwana domain, in Ise. Munetsugu stayed on in Shirakawa for a time; around 1829 he moved to Kuwana without managing to enter its service and, after passing through Owari, reached Edo at the beginning of the Tenpō era.
In Edo
Between 1831 and 1834 (Tenpō 2 to 5) he added to his signature 於江都 (Kōto ni oite, “in Edo”): he was already forging in the capital. He wanted to enter the school of Katō Tsunahide (加藤綱英), who had withdrawn with a mental disorder, and trained with his younger brother, Chōunsai Tsunatoshi (長運斎綱俊). He is linked to the sword testers Iga Norishige, a retainer of the Naruse of Inuyama, and Yamada Asaemon, the shōgun’s tester.
By the second month of 1837 (Tenpō 8) he was already smith to the Kuwana domain: the date was studied by Kojima Tsutomu in the journal 刀剣美術 (Tōken Bijutsu), no. 540. In 1845 (Kōka 2), as a retainer of Kuwana, he received the title of Bizen no Suke (備前介). In the last years of the shogunate he lived with his pupils in the house of Oka Jin'an (岡仁庵), physician to the shōgun, in Azabu Nagasaka. A tradition recorded by the Japanese Wikipedia relates that when Kiyomaro settled in Yotsuya without presenting himself to him, who had lived there before, Munetsugu sent him a challenge (果たし状, hatashijō).
Meiji and Vienna
In 1871 the edict that allowed men to cut off their topknot and give up the sword (散髪脱刀令, sanpatsu dattō rei) put an end to the commissions. Munetsugu took his school to Meguro, next to the new government’s powder magazine, and worked as a gunsmith (鉄砲鍛冶, teppō kaji) until he retired shortly afterwards; his pupils each went their own way. In 1872 (Meiji 5) he was commissioned to make a sword for the exhibition, which was shown at the 1873 Vienna World’s Fair. The year of his death is not recorded in the sources consulted.
The generations
His son Sōichirō (宗一郎) took the name Munetsugu as the second generation. There is no further information on his life and work in the sources consulted.
Among his pupils, the Japanese Wikipedia names Tairyūsai Sōkan (泰龍斎宗寛, Tairyūsai Sōkan) and Tomono Yoshikuni (友野義国). According to Toryu-Mon, Sekiguchi Norikane, a smith of Mito, learned Bizen-den from him.