Kunitsugu was a pupil of Rai Kunitoshi and grandchild of Kuniyuki. He is said to have been the cousin of Kunimitsu, and some old documents indicate that he was a pupil of Masamune. A later smith working around the 1360s is referred to as Rai Kunitsugu II. The bright hada, rich in jinie, and the clearly defined nijuba are characteristics of Kamakura Period Yamashiro work. The sword is attributed to Rai Kunitsugu on the registration document.