Adopted by Iwai Tairazaemon, Masatoshi was the career-long head of the Kasokan Shuku Barrier Gate Township.
He lived at Ryuhara "Willow Field" in Edo. He learned and worked along the greatest smiths of the ShinShinto, Hosokawa Masayoshi, then Naotane and also made swords with Kiyomaro. Gaining full mastership, he lived and worked with Masao. His swords are Kiyomaro style, many resembling those of Masao.

Wide Motohaba with an elongated Kissaki on "Great, powerful and excelling" sword blades. Jitetsu is Itame Hada where the Itame has much Jinie. There will be Nie on Gunome-Midare Ba with Sunagashi and Kinsuji in great abundance.

Tightly Knit Ko-Mokume Itame shows Jinie on bright, well-worked steel.
A storm of Obusa and Juka Choji-Midare stands proudly in an undulating, Hiro-width Yakiba that shows a profusion of strong Nie throughout.
Nakago, and the whole of the sword appears as an old Koto, having four Mekugi-ana and appearing as O-Surage Nakago. In fact several appraisers placed Kantei of this piece, before polish, as Nambokucho in origin.
The color and shape are excellent and appears as an old sword.