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Lethal Lunacy

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Episode 10

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Alternate Title Fighting Fire with Fire
Kanji 以毒制毒
Romaji Idoku Seidoku

Lethal Lunacy (以毒制毒 Idoku Seidoku) is the tenth episode of the anime series Samurai Champloo. It aired in Japan on July 22, 2004 and July 16, 2005 in America.


The episode opens at night on a samurai being challenged to a fight by a mysterious stranger who manages to kill him with one quick strike.

Fuu Jin and Mugen cleaning up the dojo.

The next morning, Mugen, Fuu, and Jin are wandering and starving as always when they encounter a priest who generously offers them food and housing… in exchange for doing chores and busywork around his place of residence. While Fuu is out running errands, she encounters a group of people discussing a string of mysterious killings where the victims are all skilled samurai, with a bounty of 10 ryō being offered for his capture. (1 Ryo in Ancient Japan is 120,000 yen or $1054.50 in America).

Fuu brings the news to Mugen and Jin, but only Mugen seems interested in the offer, so the two of them leave to find more information as Jin is left to finish the chores. The two ask around town and eventually pick up a possible lead, with Mugen tracking down the strongest samurai in the area to assure that he’ll eventually run into the mystery killer. Mugen’s lead turns up a dead end as the samurai he tracks down turns out to be a total wimp.

Meanwhile, Fuu receives some peculiar details about the mystery killings: namely, the victims bleed excessively from their orifices despite the apparent absence of any sword cuts on their body. When sunset rolls around, a group of samurai encounter the mystery killer on a bridge looking for a fight, but he refuses. When confronted further, he’s given no choice but to kill one of the men, scaring off the rest as Mugen happens upon the trail of blood left behind. Jin cuts logs, and one of the logs fly toward the priest, but the priest catches it without looking, making Jin suspicious.

Mugen and the mystery killer.

At night, Mugen hits up a small place to get a drink, and the mystery killer is sitting right next to him, with Mugen being completely unaware. The man shares his sake with Mugen as Mugen recounts the details of the mysterious killings. The two leave the bar as the mystery killer recites a story about a mountain climber who became a demon, and as the two are about to part ways, Mugen finally catches on to his identity. The two get into a brief fight as Mugen manages to narrowly dodge his attacks before the killer escapes to avoid capture, but not before promising that the two will meet again on the next full moon.

Shoryu and Mugen fight

Back at the priest’s house, he’s relaxing in a hot tub as Jin and Fuu observe, and Jin, suspecting something is up with him, takes an opportunity to attack the man who narrowly dodges the sword strike. Mugen shows up as everyone observes the cut marks on his hands, and while reciting the story, the priest (named Zuikō) chimes in and names the man as Shōryū, apparently once a student of his. He begins reciting the backstory of Shōryū to our heroes.

Shoryu's Backstory

He was originally named Ukon, one of Zuikō’s top students, and was sent on a mission overseas which went awry after a storm destroyed the boat and killed nearly everyone except for him. Ukon washed up on the shores of China (back in the day, Japan didn't know where China was) and was rescued by a group of Shaolin monks who took him in and trained him to learn a martial art style called Hakkei. 10 years later, he returned to Zuikō’s dojo, now a changed man because of his experiences in China.

Choosing to go by Shōryū (Shoryu), he became a ruthless intimidating individual who cared more about using his newfound skill for killing than anything else, even going so far as to murder a fellow unarmed student in cold blood during a training session. Getting banned from the dojo, he went on to seek mentorship from other dojos, but he got rejected from each one. Growing spiteful at the world’s inability to recognize his perceived greatness, he began murdering dojo masters to assert his own power. The priest explains that Shoryu uses a technique called ki, a force of energy that can be utilized as a weapon. When Shoryu weaponized chi, it can cause cuts to the body without even touching them.

The next day, Mugen, seeming uncharacteristically disciplined, begins training in a multitude of ways to prepare himself for his next showdown with Shōryū. Fuu is confused on why Mugen is quiet, but Jin reveals that Mugen only acts like this when Mugen doesn't think he could win. When nightfall comes, Mugen goes out for a walk, meeting up with Shōryū on the bridge from earlier. The two begin to fight, with Mugen proving himself a worthy challenger for Shōryū as they eventually manage to knock each other’s swords out of their hands. Mugen, feeling weak from Shōryū’s attack, is just about to receive the death blow, but as soon as Shōryū gets up close and personal, Mugen pulls out a small blade and uses it to stab Shōryū in the chest, killing him (similar to how Shoryu killed an unarmed student) while Shoryu's teacher senses Shoryu's death..

Mugen kills Shoryu



  • This marks the first time ki is referenced.