Origin

Many years ago, Takeshi Tatsuo was a leader of a peaceful clan called the Foot. One day, chaos emerge from the depths. To save his clan Tatsuo made a deal with an oni, which it was a Krang, with a powerful suit of armor that would make him invincible. But the armor corrupted his soul turning Tatsuo into a terrible nightmarish demon called the Shredder. Karai, Tatsuo's daughter developed the Hamato clan to fight him. Karai sacrificed herself to banish Shredder and herself into the Twlight Realm.

500 years later, when Yoshi is a child, his mother Atsuko left to defend the world when the Shredder will return. Yoshi was left alone with his grandfather Hamato Yuuta and he was never been the same ever since.

As an adult Yoshi, became a movie star that goes by the name Lou Jitsu. There he meets Big Mama who was watching him. They went on a date together for the next few days until one night when Yoshi talks to her into marrying her Big Mama reveals herself as a Jorogumo Yōkai and captures him to make him fight many monsters at Battle Nexus where he met Tang Shen, Oroku Nagi, and Nagi's little brother, Oroku Saki.

As they were counting down the days, Yoshi found a rat squeaking around for food. Yoshi gave it some cheese, and named it Splinter. Splinter, now his pet rat, would enjoy mimicking Yoshi's martial arts movements, forming the basis for his knowledge of Ninjutsu.

Oroku Nagi and Hamato Yoshi began to clash against each other, since they found out of their heritage. Oroku Nagi was from Takeshi Tatsuo's Foot Clan and Hamato Yoshi was from Hamato Karai's Hamato Clan. They also clashed over the love of Shen, who loved Yoshi. When it became clear that Tang Shen loved only Yoshi, Nagi savagely beat her. She was saved by Yoshi, who in a moment of rage, killed Nagi with his bare hands.

During a Battle Nexus fight, Yoshi, Tang Shen and Splinter fled to New York City, where he founded a small martial arts school called Lou Jitsu School of Ninjutsu. Meanwhile, the Foot continued to train Nagi's younger brother, Oroku Saki after he escaped many years of fighting in Battle Nexus. Fueled by a thirst for vengeance, Saki eventually became a high-ranking member of the organization, and was tasked with leading a branch of the Foot in New York. Once there, Saki adopted the mantel of the Shredder and led the clan to the highest ranks of the underworld, specializing in burglary, espionage, and assassination. Yet the entire time, Saki sought the opportunity to avenge his brother by slaying Hamato Yoshi.

One night Yoshi returned home to find his apartment ransacked, Tang Shen lying dead on the floor. Yoshi then saw the Shredder, who, revealing his identity as Oroku Saki, promptly killed Yoshi with his blades. Yoshi's pet rat scratched up Saki's face, forcing Saki to wear the Kuro Kabuto over his head. Alone and heartbroken, Splinter escaped into the sewers, rummaging for food to survive.

15 years ago, a young girl was carrying four baby turtles home from the pet shop. A blind man was crossing the road when a truck labeled "T.G.R.I." almost ran him down. A young man behind the girl with the Turtles ran out to save the blind man, bumping the girl with the turtles and knocking the jar from his hands. The jar broke when it landed in the gutter, and the Turtles were washed down a sewer drainage grate. As the truck swerved, the back doors flew open. A container of green glowing goo fell out and was subsequently washed down the drain with the baby turtles. The turtles landed safely, until the jar of goo fell beside them, coating them with its contents.

Moments later, Splinter came across the babies, finding them swimming in ooze in a pizza box and gathering them into a can. He didn't realize he was coating himself with the green goo as he gathered them up. In very little time, Splinter and the turtles evolved and mutated into anthropomorphic beings with intelligence and emotion rivaling that of a human. Their mutation near completion, and educated, the rat named the Turtles after Renaissance artists - Leonardo, Donatello, Michaelangelo, Raphael. For the next fifteen years, Splinter raised and instructed the young turtles, his sons, in the martial arts in order avenge his master.

It is later revealed that the ooze was created by a group of benevolent aliens known as Utroms than stolen by a malicious group of Utroms called the Krang.