Shin Shinkage Ichiden Ryū 新神陰一円流 was founded by Nonaka Shinzō Naritsune who was a disciple of Kamiizumi Nobutsuna. Kamiizumi was the founder of the famous Shinkage Ryū which spawned many schools of swordsmanship in later years. Shin Shinkage Ichiden ryū placed importance in its technique on the ideas of circularity in swordsmanship. It is the syncretic arts of Shinkage-ryū and Ichiden-ryū that gives Shindō Munen-ryū and Shinkan-ryū its unique style in kenjutsu.
Fukui Hyoemon's original art of Munen-ryū, later to be called Shintō Munen-ryū incorporated many ideas from the art of Shin Shinkage Ichiden-ryū. The methods of Shin Shinkage Ichiden-ryū were kept in the Nonaka family for a few generations. The style no longer exists except within the flavors of the Munen-ryū and Shinkan-ryū Kenpō.