Kantei
Black-and-white photograph made up of five strips: both faces of the point, a stretch of blade, the tang with two holes and the two-character signature, and the whole blade, curved.

Bizen · Ko-Bizen · the Juzumaru

Ko-Bizen Tsunetsugu (古備前恒次)

The swordsmith of the Juzumaru, one of the five swords under heaven, and a name shared by Bizen and Bitchū: what is known, what is tradition and his sources

Tsunetsugu (恒次, Tsunetsugu) is a name borne by swordsmiths of the Ko-Bizen (古備前, Ko-Bizen), in Bizen, and of the Ko-Aoe (古青江, Ko-Aoe), in neighbouring Bitchū. His fame comes from the Juzumaru (数珠丸, Juzumaru), one of the five swords under heaven: tradition gave it to the Tsunetsugu of Aoe, and today it is attributed to the one of the Ko-Bizen. Almost everything known about him is what is known about that blade.

Tsuchiura City Museum and Agency for Cultural Affairs, via Bunka Isan Online

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The Juzumaru, among the tenka goken (天下五剣)
83.7 cm
Length of the Juzumaru (Japanese Wikipedia)
1922
Designated National Treasure, the rank of the time
On this page
  1. Quick profile
  2. In short

Quick profile

Name
Tsunetsugu; he is called Ko-Bizen Tsunetsugu to tell him apart from the Tsunetsugu of the Aoe of Bitchū AT
Kanji and reading
恒次 (Tsunetsugu) · 古備前恒次 (Ko-Bizen Tsunetsugu) AT
Period
The Ko-Bizen runs from the end of the Heian to the middle of the Kamakura. The Japanese Wikipedia, in giving the NBTHK’s conclusion on the Juzumaru, places him as active in Bizen at the end of the Kamakura. AT
Province
Bizen AT
School
Ko-Bizen, the oldest Bizen school AT
Master and generations
Satō Kanzan proposed that the Tsunetsugu of the Juzumaru was the one of Bizen, son of Masatsune of the Ko-Bizen. The record of an Aoe tachi at the Kyūshū National Museum says that there were several Tsunetsugu in Aoe. AT
Documented fact and tradition
Documented: tachi signed “Tsunetsugu” with their official record, such as the one at the Tsuchiura city museum, Important Cultural Property. Tradition: that the Juzumaru was from Aoe and that it was Nichiren’s sword. AT

In short

What we know. The Juzumaru is a tachi signed “Tsunetsugu”, Important Cultural Property (重要文化財, jūyō bunkazai), kept by the Honkō-ji temple in Amagasaki. There is also a tachi signed “Tsunetsugu” of the Kamakura period, Important Cultural Property since 1950, at the Tsuchiura city museum, whose record does not say which school it belongs to.

How we know it. Almost everything comes from the Japanese Wikipedia, which summarises the tradition, Satō Kanzan’s proposal and the NBTHK’s conclusion. The records of the Agency for Cultural Affairs document the tachi of Tsuchiura and of Aoe.

What we do not know. His dates, the text of the NBTHK’s study and the official record of the Juzumaru.

Sections

  1. Ko-Bizen and Ko-Aoe · from Aoe to Bizen · Nichiren Life and times Why there are several Tsunetsugu, how the Juzumaru passed from Aoe to the Ko-Bizen and the story that links it to Nichiren.
  2. Ko-itame · midare-utsuri · nakago ubu Work and style What the sources say of the blade of the Juzumaru, the traits of the Ko-Bizen and how a Tsunetsugu of Aoe signs.
  3. Tenka goken · meibutsu · jūyō bunkazai Famous works The Juzumaru, the tachi of Tsuchiura and the Aoe blades that bear the same name.
  4. Bibliography Sources The sources consulted on 4 October 2026, with their link, and the credit for the image.