Kunitomo is transmitted as the eldest of six brothers born to Kuniie, the celebrated progenitor of the school in Yamashiro Province. His younger brothers were Hisakuni, Kuniyasu, Kunikiyo, Arikuni, and Kunitsuna. Together with Hisakuni and Kuniyasu, Kunitomo was summoned to serve as a (appointed palace smith) to Retired Emperor Go-Toba, placing him at the very center of early courtly sword production. Traditional sources date his activity to the Jokyu era (1219-1222), and he is said to have styled himself Tobayashi Saemon.
Kunitomo's works are distinguished by a slender form exhibiting pronounced and , terminating in a refined that conveys the restrained elegance characteristic of early production. The forging is a tightly knit presenting a (pear-skin) surface quality, with fine adhering well and visible within the ground steel. The temper line is predominantly with subtle , , and ; the is deep and bright, with attaching beautifully and and appearing throughout. In certain areas the displays a soft, -like quality that lends further depth to the temper.
Securely authenticated works by Kunitomo are exceedingly rare. The signed preserved at Atsuta Jingu, designated an Important Cultural Property, stands as the principal point of reference, and the few other surviving examples are noted for their close resemblance to it in both workmanship and signature style. Taken together, these blades superbly manifest the elevated dignity and refined aesthetic of the early school, placing Kunitomo among the most distinguished smiths of the formative tradition.