One of the rare Tokyo blacksmith who is still in production. Tanaka Ichirou is the blacksmith for Osahiro brand. He is over 80 years old, so he has once retired but there were so many carpenters requesting him to make chisels and plane blades, with his wife's persuasion he has come back, and producing tiny amount of chisels and plane blades.

Sotomaru is a carpenter style gouges where the steel is laminated on the outside of the blade. Uchimaru style can be seen on Konobu's gouges, and those are usually used by the sculptors.