His works are often compared with those of the other great Koto era (987-1596) swordsmiths including Sōshū Masamune, Toshiro Yoshimitsu, Go Yoshihiro, Bizen Nagamitsu, and Ike Muramasa.
[4][5] After leaving Gōshū province to go to what is now Kanagawa Prefecture, Sadamune became a student of Masamune, sometime around the Namboku-chō[5] era.
As a mark of his completion of his teacher's training he inherited the mune part of his name Sadamune from Masamune.
Legend says he returned home to produce a copy of a famous sword called the Ropecutter.
[10][11] Higo Munekage (Higo No-Kuni Kumamoto-Kishi, Hagi Jiemon No-Sho Fujiwara Munekage Saku) who was a student of Suishinshi Masahide takes a great influence from Sadamune in his work, but wasn't a student of his.Higo Munekage Katana Kokon Mei Zukushi and other books listing Japanese sword smiths and blades list Motoshige as a student of Sadamune however Dr. Honma Junji disagrees with this in his book Nihon Koto Shi (History of Koto) By Dr. Honma Junji