The Foot Clan debuted in the first issue of Mirage's Teenage Mutant Ninja Turtles as a parody of a similar organization from Marvel's Daredevil, The Hand.
During a time traveling adventure to feudal Japan, Raphael meets two men called Sato and Oshi and teaches them Ninjitsu. After the turtle and his brothers return to the present the two men vow to never mention the strange shelled creatures they encountered. They predict that they and others that join with them will become a force to be reckoned with and because every journey starts with a single step they poetically call themselves "The Foot".
The Shredder's Leadership
By the 1980's The Foot had become the most feared Clan of assassins in Japan. When a member called Hamato Yoshi killed a fellow member Oroki Nagi over a feud involving a woman Yoshi brought dishonor and was given a choice by the clan to end his own life and hope for honor in the next or exile. Yoshi chose the latter option taking his love Tang Shen and his pet rat to New York to start a new life. Nagi's younger brother Saki vowed vengeance on his brother's killer and was adopted by the clan who used the Saki's anger to bend him to their will, and over the years rising up the ranks to become the fiercest warrior.
At a mere eighteen years of age the leaders chose Saki to lead a branch of the Foot in New York. Within a year now calling himself the Shredder had turned the New York Foot into formidable criminal empire involved in drugs smuggling, arms running an assassination. Saki as the Shredder sought out Yoshi and Shen and killed them both in cold blood.
Fifteen years later the Shredder was challenged to a dual to the death to avenge Yoshi. Arriving at the specified location Shredder was surprised to find that his challengers were four giant turtles. The turtles battled with a group of Foot Ninja, swiftly defeating them but not without incurring injuries of their own. Challenging the turtles himself, they were no match for the Shredder until Leonardo managed to plunge his katana through the Shredder's torso. Incapacitated the Shredder asked the turtles to "finish it" but the turtles offered the human the opportunity to restore his honor by killing himself.
Taking out a thermite grenade he vowed that if he was to die he would take the turtles with him, Donatello quickly used his bo staff to send Shredder and his grenade over the rooftop as it exploded killing the Shredder. Nearly a later on Christmas Eve had managed to track down the whereabouts of turtles now living in an apartment with their friend April O'Neil, the full force of the Foot Clan engaged in a battle with Leonardo on the rooftops of New York. The turtle managed to hold his own until he the arrival of a familiar cloaked figure.
Dropping him through April O'Neil's window the battered turtle revealed that the Shredder had returned. Shredder and the Foot invaded April's apartment and antique shop below fighting a fierce battle with the turtles, Splinter and Casey Jones. When the building caught fire and police sirens could be heard the Shredder ordered the Foot to retreat but warned the his enemies to watch their backs. A year on the Foot had once again expanded their criminal empire setting up multiple complexes in the city's sewer system system with the Foot using the Sewers to move about the city undetected. After their exile in Northhampton the turtles return to New York.
Finding one of the Foot's underground complexes Donatello uses their computer to locate their main surface head quarters which was a hollowed out city block. Along with their Triceraton ally Zog the turtles managed to infiltrate the a Foot's Head Quarters battling their way through Foot Soldiers. The turtles encountered more resistance when the encountered three genetic monsters dressed like the Shredder that swiftly killed Zog. The turtles battled the monsters that were joined by the Shredder's Elite Guard and more Foot Soldiers while Leonardo went off to confront the Shredder alone.
Before battling the turtle, the Shredder revealed that Foot's knowledge of science and magic allowed them to bring him back to life using a colony of worms that fed on remnants of Saki which would take the form of what they fed on, interlocking and forming together. Shredder and Leonardo battled on the roof top while the rest of the turtles inside try using the Foot's high tech machinery against them, including launching a missile into a tower containing deadly chemicals causing massive explosion destroying the building as Leonardo decapitates the Shredder.
Back in the sewers Leonardo carries the corpse of Oroku Saki. The four turtles hold a funeral pyre were the burn Saki's body to honor their enemy and to make sure he can never be resurrected again. While this would be the end of Saki's leadership the Foot Clan would survive to menace the turtles again.
City At War
Years after the Shredder's demise the Foot fell into disarray. Without strong leadership the clan split into factions all of which fought for control. The war began to become heated as the factions would battle on the streets and even bomb buildings which housed members of rival factions all the while innocent civilians would be continually caught in the middle.
The war caught the attention of the turtles who once again returned to New York to confront the Foot. A confrontation with the Foot and two of their giant robots on the streets in broad daylight Leonardo realized that the Foot were fighting each other as well as them and was shocked at the level of violence which escalated when the Police and swat teams were called in. One of Shredder's Elite Guards managed to track down the turtles but was maimed by Raphael, the ninja said that they were duty bound to slay Leonardo for killing the Shredder and then promptly killed himself.
For some time the war was being observed by another group led by a mysterious female ninja. Tracking the turtles to their new hide out she had her warriors attack them and kidnapping Leonardo leaving a note for the other turtles with a phone number. Arranging to meet, the turtles arrived at Karai's base to find their brother was not a prisoner. The female ninja introduced herself as Karai, leader of the Foot in Japan who had come to restore order to the New York Foot. She explained that even before Shredder's death the ties between the Japanese and the New York Foot were practically nonexistent.
She wanted to enlist their help in killing the Shredder Elite which would be a crucial move in her taking control offering the turtles a truce if they helped her. The turtles took time to consider Karai's offer soon arriving at the conclusion that unless the accepted her offer they would always be at war with the Foot. Returning to Karai's base they saw that there had been a raid by a rival faction and that Karai's daughter had been killed. The turtles accepted Karai's offer to help kill the Shredder Elite.
To help lure the elite out Karai dressed in the armor of the Shredder and allowed the ninja to follow her to the remains of April O'Neil's building. There she tried to convince them that she was Saki and that the should commit sepuku. Only one of the elite fell for the trick killing himself immediately but the rest remained unconvinced. It was then that she revealed her true identity and that she had lured them into a trap. The turtles emerged from hiding and a fierce battle ensued in which the turtles and Karai proved victorious. Karai told the turtles that she owed them but Leonardo assured her that she owed them nothing but her word of truce between them and Foot. Karai stated her intention to stabilize the Foot and return to japan and scatter her daughters ashes.
Currently the Foot in New York is led by Karai. When the Utroms arrived on Earth and set up a base in upper New York Harbor they wished for a security to be unarmed and the Foot won the contract due to their skills at empty hands fighting. This unsettled the turtles particularly when a sparring session between Leonardo and his rival Cha Ocho in the base's gym got out of hand.
Leonardo joined the Foot to help with a security problem of their own. Karai revealed to the turtle that all the branches of the Foot throughout the world had been decimated by mysterious warriors and that the New York Foot was the only branch left. Managing to kill one of the warriors an examination revealed that despite looking male it was actually genderless and used weapons similar to those used by ancient Aztecs but most perplexing of all it carried a mass minted coin that had Al Gore as the president on it.
Leonardo helped the Foot capture one of the warriors alive. The warrior talked as if the Foot Clan were a threat and referred to Foot spreading an book of evil power. Before the warrior could be executed it killed itself by snapping his own neck. The turtle noticed that as one of their side projects the Foot were publishing a book of spells. This made Leonardo suspicious but Karai tried to reassure him that it was harmless nonsense that is sold new ageists but upon inspection Leonardo recognized the content as reminiscent of real spells he's encountered before. This made him determined to find out the full truth.