We covered Itto-ryu as a whole in School #5 of this series — its founder Ito Ittosai’s 33 undefeated duels, the brutal succession duel that produced Ono Jiroemon Tadaaki, and the Nakanishi branch’s role in developing bōgu-and-shinai training. This week we focus on the senior surviving branch of that entire family: Ono-ha Itto-ryu, which has transmitted the original teachings of Itto-ryu in their most direct and unbroken form for over four centuries. The school that taught the Tokugawa shoguns is still active today, in the same city, under its 18th headmaster.

Tadaaki’s story begins with his previous name: Mikogami Tenzen. Born in 1565, he was one of Ito Ittosai’s two most advanced students — the other being a man named Ono Zenki. When Ittosai decided it was time to name a successor, he did something almost unthinkable: he ordered the two men to fight each other to the death. Tenzen won. He was so grieved at killing his training partner and friend that he took the dead man’s family name out of tribute, becoming Ono Jiroemon Tadaaki. That moment of grief-driven renaming is where both Ono-ha Itto-ryu and its name originate.

Tadaaki’s swordsmanship brought him to the attention of the Tokugawa family. He was appointed alongside Yagyu Munenori as one of only two official kenjutsu instructors to the shogunate — serving both the second shogun Tokugawa Hidetada and the third shogun Tokugawa Iemitsu. One account captures his uncompromising character: during a lesson with the shogun, Tadaaki reportedly ripped away the carpet the shogun was sitting on, causing him to stumble. He then delivered his critique. The shogun was reportedly not pleased, but the lesson was delivered anyway.

It was said that Tadaaki was Yagyu Munenori’s superior in actual swordsmanship, but that his severe, uncompromising character made him the less politically favored of the two. The contrast between the two official shogunal instructors is striking: Munenori wrote philosophical treatises on strategy and governance; Tadaaki threw carpets. Munenori became a daimyo; Tadaaki became a legend among swordsmen.

One important historical detail: the school was not formally called “Ono-ha Itto-ryu” during Tadaaki’s own lifetime. The name was formalized under the third headmaster, Ono Tadatsune — Tadaaki’s son — who established the Ono branch identity as distinct from other Itto-ryu lineages. Tadaaki himself is counted as the first headmaster of this line and its effective founder, but the “Ono-ha” designation crystallized one generation later.

This principle is embodied most completely in Ono-ha Itto-ryu’s signature technique: kiriotoshi (cutting down). Rather than parrying an incoming strike and then counter-attacking — the two-move response — kiriotoshi simultaneously deflects the opponent’s blade and delivers the decisive cut in a single motion. The technique requires absolute commitment and precise timing. When executed correctly, it dissolves the distinction between defense and offense entirely. This is the literal expression of “one sword is ten thousand.”

The kiriotoshi principle exerted a direct influence on modern kendo’s tactical and competitive culture. The debana waza — counter-strikes timed to catch an opponent just as they initiate their own attack — that advanced kendo practitioners cultivate today trace their conceptual lineage directly to this approach.

Ono-ha Itto-ryu’s curriculum consists of 170 techniques taught as kumitachi — partnered paired forms using wooden swords. The curriculum is organized into several sets:

Training uses wooden swords throughout — odachi (long sword) and kodachi (short sword). Unlike the Nakanishi branch, which adopted bōgu-and-shinai sparring and shaped modern kendo’s training culture, Ono-ha has maintained a kata-only approach, preserving the original technical intent without modification for a competitive context.

The school’s transmission across 18 generations is one of the longest unbroken koryu lineages in Japan:

• Ono Tadaaki — 1st headmaster, d. 1628
• Ono Tadatsune — 2nd headmaster (formalized the school’s name)
• Ono Tadao — 3rd headmaster (served three shoguns)
• Tsugaru Line — 4th headmaster established the Aomori branch
• Sasamori Junzo — 16th headmaster (founded Reigakudo)
• Yabuki Yuji — 18th headmaster, current, b. 1970

A notable detail in this lineage is that the third headmaster, Ono Jiroemon Tadao, served as official kenjutsu instructor to three successive shoguns: Ietsuna, Tsunayoshi, and Ienobu. This extended the school’s Tokugawa service for another full generation beyond Tadaaki’s own tenure. Furthermore, the fourth headmaster, Tadakazu, passed the complete system to Tsugaru Nobumasa of the Hirosaki Domain in Aomori Prefecture, establishing a Tsugaru line that would eventually bring the school to the Sasamori family.

The 16th headmaster, Sasamori Junzo (1886–1976) was a remarkable figure in his own right: a kendo practitioner, Christian minister, statesman, and educator who served in the Japanese Diet. In 1965, he published Itto-ryu Gokui, a comprehensive manual of the school. This was an almost unprecedented act of transparency for a koryu school, made possible by his philosophy that serious practitioners should be able to see and understand a school before committing to join it. The Reigakudo has maintained this openness ever since.

The current 18th headmaster, Yabuki Yuji (born 1970), became a direct student of the 17th headmaster, Sasamori Takemi, in 1998 and was formally named headmaster on October 1, 2017. He holds a 7th dan kyoshi in kendo alongside his koryu responsibilities—a rare combination that connects the old tradition directly to modern Japanese swordsmanship practice.

The physical home of Ono-ha Itto-ryu today is one of the most quietly extraordinary spaces in Japanese martial arts: the Reigakudo dojo in Daizawa, Setagaya, Tokyo — housed inside a Methodist church. The combination is not accidental. Sasamori Junzo was himself an ordained Christian minister, and the school he led and the faith he practiced shared the same physical space. The Reigakudo Foundation now continues the school’s transmission following his son Sasamori Takemi’s death, under Yabuki Yuji’s direction.

It sits not far from where Ono Jiroemon Tadaaki himself taught the Tokugawa shoguns four hundred years ago. That the school still meets in the same city, in an unbroken line, is itself an extraordinary fact.

One final thread worth noting for readers who come from an aikido background: Morihei Ueshiba, the founder of aikido, studied under Sokaku Takeda of Daito-ryu Aiki-jujutsu. Sokaku Takeda — as we noted in School #8 — trained under Sakakibara Kenkichi of Jikishinkage-ryu. But Takeda also studied Ono-ha Itto-ryu. The line from Ono Tadaaki’s kiriotoshi principle runs, through multiple transmissions, directly into the technical foundation of one of the world’s most practiced martial arts.

• One of only two official sword schools of the Tokugawa shogunate, alongside Yagyu Shinkage-ryu—a status maintained across three successive headmasters and three successive shoguns
• The kiriotoshi technique—the simultaneous cut-and-deflect—directly influenced modern kendo’s debana waza and counter-attacking tactical culture
• Nakanishi-ha Itto-ryu and Mizoguchi-ha Itto-ryu both descend directly from the Ono-ha lineage, making this school the root of the branch most responsible for the development of bogu-and-shinai training
• Yamaoka Tesshu, one of the 19th century’s most celebrated swordsmen, Zen practitioners, and calligraphers, trained in Ono-ha Itto-ryu and used its principles as the foundation for his own Itto Shoden Muto-ryu
• Sasamori Junzo’s 1965 curriculum book remains the most comprehensive public documentation of any koryu school’s technical system—a historically unprecedented act of openness
• Recognized by both the Nihon Kobudo Kyokai and Nihon Kobudo Shinkokai as one of Japan’s authentic classical martial arts
• Active today at the Reigakudo in Setagaya, Tokyo, with authorized branch dojos in the United States (Southern California and Northern California)

Of all the schools in this series, Ono-ha Itto-ryu may have the strongest claim to an unbroken thread connecting the present to the most violent and consequential period of Japanese history. Its founder won a duel to the death to inherit a system. He then taught the rulers of Japan. His successors served three more shoguns. The school survived the fall of the shogunate, the Meiji transformation, two world wars, and the complete modernization of Japanese society — and today meets in a church in Setagaya under a headmaster who also holds a 7th dan in kendo.

The central teaching—one sword is ten thousand swords—turns out to be literally true in another sense: this single lineage seeded Nakanishi-ha, Mizoguchi-ha, and ultimately the entire modern kendo tradition. One school, ten thousand practitioners worldwide, four centuries of unbroken transmission.

• Wikipedia — Ono-ha Itto-ryu — en.wikipedia.org/wiki/Ono-ha_Itto-ryu. Core lineage, headmaster succession, curriculum overview, and Reigakudo founding.
• Wikipedia — Mikogami Tenzen (Ono Jiroemon Tadaaki) — en.wikipedia.org/wiki/Mikogami_Tenzen. Biographical detail on the founder, the succession duel, and the Tokugawa appointment.
• Budo Japan — “Ono-ha Itto-ryu: One Sword to Rule Them All” — budojapan.com. Practitioner account of training at the Reigakudo; interview with 17th headmaster Sasamori Takemi. Source for the Methodist church dojo detail, the 1965 curriculum book, and the school’s openness policy.
• Budo Japan — “Kiriotoshi: An Invincible Technique Born on the Battlefield” — budojapan.com. Interview with 18th headmaster Yabuki Yuji. Confirms biographical details (born 1970, named headmaster October 1, 2017) and the itto sunawachi banto principle.
• Buyens, Guy — “Ono Ha Itto-ryu: An Introduction” (July 2022) — onohaittoryu.be. Detailed lineage document covering the third headmaster Tadao’s service to three shoguns and the Tadaaki carpet-pulling anecdote.
• Caile, Christopher — “Itto-ryu Kenjutsu: An Overview” — fightingarts.com. Overview of all Itto-ryu branches and their derivation from the Ono-ha lineage.
• Ono-ha Itto-ryu USA — ittoryu.org — Official U.S. branch website. Confirms the 2012 opening of the first authorized U.S. study group and current branch locations under 18th headmaster Yabuki Yuji’s authority.
• Sasamori, Junzo; trans. Mark Hague — Secrets of Itto-ryu, Book One (2023). English translation of Sasamori Junzo’s 1965 curriculum text.