Koto Period is from the late Heian-era until Momoyama-era (Bunroku-era文禄 1596).

Watetsu (和鉄the highest quality steel called Tamahagane) is used from Heian-era

until Oei(応永1428). Kazuuchimono数打物(the worst quality Katana) is produced

from Eiroku-era (永禄1558) until Tensyo-era (天正1592) for 34 years.

Quantity was regarded as more important than quality for Kazu-uchi-mono swords.

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In Koto Period, I love Bizen-style.

Yoshifusa(吉房): National Treasure Tachi Signed 吉房, middle Kamakura Period 13th century, in Tokyo National Museum. This is an outstanding example by Yoshifusa in the Fukuoka-Ichimonnji school.

Yoshifusa is the finest leading swordsmith of the school. His ability to forge swords with plump well-developed Choji and wide Nioi, regulary and consistently, puts his name at the top of the list of those producing gorgeous Bizen swords.