Toshihira Osumi was born in 1932, in Ota, Gunma Prefecture. His real name is Sadao Osumi. He was designated a Living National Treasure for his 'to-kaji' technique.

In 1952, Osumi became apprenticed to Akihira Miyairi (another Living National Treasure) and studied the craft of katana swordmaking. When he was 28, Osumi became independent.

He energetically entered competitions held by the Japanese Fine-Art Sword Preservation Association. In the first two competitions, he won a prize for effort. But from the 3rd to 8th competitions, he won a special prize. Finally, on the 10th, 12th and 14th times, he won the Manamune prize, which is the highest prize of all. Despite winning many prizes, Osumi is not proud. He believes that the implications of craftsmen are deliberated through their pieces.

In 2001, Osumi presented an amulet sword to Princess Aiko, the Princess Toshi. Moreover, he has dedicated many other pieces to places like Ise Shrine and Ota District.