小次郎

Kojirō

Kojirō is the swordsman Musashi met on a small island in the strait between Nagato and Buzen. The oldest account calls him only Ganryū, and no source records his age, face or home.

Life

Not recorded

Notes on the dates below

Evidence

Probable

How sure the record is that he lived and did this

Probable

Episodes

Duel record

One bout on record, against Musashi at Funashima. The accounts disagree on how it ended.

Probable

Born: Not recorded. His age at the duel is unknown. A claim that he was 18 comes from 1776 and is legend.
Died: The 1654 monument says he died at Funashima, about 1612 by later tradition. A record of 1672 tells the ending differently.
Side: Taught the Ganryū school (1672 record)

Who he was

Traditional · Later accounts

The oldest account, the 1654 monument, calls him only Ganryū (岩流), "a master of strategy". A family record of 1672 gives a name: Kojirō (小次郎). It describes him as a teacher of the Ganryū school with pupils of his own.

The full name Sasaki Kojirō is later. A play of 1737 has "Sasaki Ganryū". A note in a book of 1776 gives Sasaki Kojirō. Other books give him other surnames, including Tsuda in 1727. The series calls him Kojirō and does not treat Sasaki as settled history.

No source records his age, his face or where he came from. The claim that he was 18 is from 1776 and is legend. Birthplaces claimed for him are local traditions with no early source.

The film shows a composed man of about forty in a pale robe. That is a design choice. No likeness from life exists.

The road to the fight

Traditional · Later accounts

The record of 1672 says Musashi came to Buzen as a teacher of two-sword fighting. Kojirō was also teaching there. Their pupils argued over whose master was better, and the two agreed to settle it. They also agreed that no pupil would come. The project has seen this record only through modern quotations.

The 1654 monument gives the terms. Ganryū asked for real blades. Musashi answered that Ganryū should use a bare blade and all his art, and that he would carry a wooden blade and show his secret. They sealed the agreement.

Who first asked for the fight is unclear. The monument's sentence has no stated subject, and modern readers disagree. So the series says "the two agreed".

The date is not recorded. The year 1612 first appears in 1755. Books also give 1602 and 1601.

The island

Traditional · Later accounts

The 1654 monument places the meeting on an island in the sea between Nagato and Buzen, called Funashima. The two men met there "at the same time". Nobody was late. Musashi's late arrival first appears in a book of 1755.

Ganryū came holding a bare blade of "three shaku". If literal, that is about 91 centimetres, but the phrase may only mean "a sword". The monument says he was careless of his life and used all his art. Musashi, with a wooden blade, killed him with one blow. "Lightning," the monument says, "was slow beside it."

It does not say where the blow landed. Musashi's own book never mentions the island or the man.

The monument also says the common people renamed the island after him. Its popular name is Ganryūjima, though its official name is still Funashima.

After, and how we know

Traditional · Later accounts

Kojirō's side of the story is almost unrecorded. The project found no writing by him, or by his school, about this fight.

The 1654 monument comes from Musashi's family. The 1672 record comes from a family in the service of the Hosokawa, outside Musashi's school, and it tells the ending differently. It was written to show why Musashi needed their help, not to tell Kojirō's story. We have not seen the manuscript.

Most of what people remember is later. Musashi arriving late, a sword carved from a boat oar, a scabbard thrown into the sea, a warning from people on the shore: none is in the 1654 monument. They appear in books written many decades later. A story of 1783 has the shore people urging him not to go. He answers that a warrior who breaks his word is shamed, and the people later make him a grave on the island. These are legend.

Sources

Kokura monument inscription (Kokura hibun), put up by Musashi's adopted son Miyamoto Iori at Tamukeyama, Kokura (1654)

Primary source · A family memorial written about nine years after Musashi died. It is not an independent witness: for the early bouts it follows his own book. The linked Kitakyushu City page is about the monument; it does not support the duel claims. The Japanese text was read in a modern reading (Fukuda Masahide, 2003, as reproduced on Japanese Wikipedia) and in the 1716 printing, not on the weathered stone.
Numata-ke Kiroku (Record of the Numata House) (1672)

Later tradition · A family record from the Hosokawa sphere, not from Musashi's school. The only early account that gives Kojiro's name and a different ending. Known here only through modern quotations (the linked Soeda town page prints a reading text); the manuscript was not seen.
Furukawa Koshoken, Seiyu Zakki (1783)

Later tradition · Records a Shimonoseki local story, 171 years after the fight, told warmly toward Kojiro. Known here only through Japanese Wikipedia; the book was not read.
Toyoda Kagehide, Nitenki (Record of Niten) (1776)

Later tradition · A later Kumamoto biography built on the Bukoden. Adds the name Sasaki Kojiro, the date in the 4th lunar month, and the age of 18 for him. Not read in full; quoted passages were read through other writers.
Toyoda (Hashizu) Masanobu, Bukoden (Life of Lord Musashi), Higo line (1755)

Later tradition · A biography written in Kumamoto about 150 years after the Kyoto fights. Source of the dated years 1596 and 1599, which are sums from Musashi's age, and of the late-arrival and killing-at-the-pine stories. Read through a modern scholar's transcription (linked; archived copy), not the manuscripts.
Tachibana (Tanji) Hokin, Tanji Hokin Hikki (also titled Heiho Taiso Bushu Genshin-ko Denrai) (1727)

Later tradition · The earliest surviving written version of the Arima story and the source of the pine fight in Episode 2. Written about 130 years after the Arima bout. Read through a modern scholar's transcription of the Yoshioka passage (linked; archived copy); the manuscripts were not seen. The date of the Yoshioka passage is inferred.
Miyamoto Musashi, Go Rin no Sho (The Book of Five Rings), Earth Scroll, opening autobiographical passage (1643-45)

Primary source · Musashi's own account, written about 47 years after his first bout. No handwritten original survives; the text comes down in copies. Read in a modern critical text with variant readings; a printed edition was not read. It proves what he claimed, not what happened.
Samurai Retold research notes on portraits and likenesses of Musashi, Arima Kihei and Kojiro (2026)

Modern work · The series' own notes on what images survive. No portrait made from life survives for any of them. The film's faces are design choices.

Appears in

Coming soon

Episode 01 · 5 min · Supporting

Musashi's First Fight

Miyamoto Musashi later wrote that he fought more than sixty times and never lost. The first, he said, was against a grown man called Arima Kihei, when he was thirteen. The episode tells that fight as a later account describes it, then shows how much of it the older sources support.

Coming soon

Episode 02 · 7 min · Supporting

The Yoshioka

In Kyoto, the Yoshioka sword school meets Musashi in three escalating contests, as told on a stone his adopted son set up in 1654. The episode then lays that account beside the other versions, including the tellings from the Kyoto side.

Coming soon

Episode 03 · Opponent

Ganryū

Two rival teachers agree to settle a quarrel on a small island in the strait between Nagato and Buzen. The episode tells it the way the oldest surviving account does, then looks at who else wrote it down.

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