Karai is usually a high ranking member of the Foot Clan.Abandoned by her parents at a young age, Karai was taken in and adopted by Oroku Saki, the Shredder. Trained in ninjutsu and an aspiring practitioner of bushido, Karai first appears as one of the highest-ranking members of the Foot Clan, similar in status to Hun; eventually, she becomes its leader. Arriving in NYC after hearing the news of the gang war taking place after the Shredder's reported demise, she quickly enlists the aid of the Turtles to stop it, promising an end to the Foot's vendetta against them in exchange for their assistance. Leonardo, convinced that Karai is honorable despite her legacy. Karai and the Foot reappear as a fully-healed Oroku Saki retakes control of the Foot. She manages to stay in the graces of both sides until the Turtles face the Shredder again in the season's finale, where she stabs Leonardo in the shoulder, damaging his carapace, although she later prevents the Utrom Shredder from killing the Turtles while they are unconscious. Despite her efforts, however, the Shredder is taken prisoner and exiled, Karai and Foot Tech Division Head Dr. Chaplin are sent back to Earth.
With her father gone and dead in the eyes of the world, Karai takes over the Foot, as well as the guise of the Shredder. Furious at what she saw as a betrayal by the Turtles, Karai spends the season plotting her revenge against them, first attacking them on the psychic plane via Foot Mystics, and later coordinating and leading an assault against them at their lair, which she believes successful. She later on faces Leonardo (who was not at the lair at the time of the assault), who defeats her but then departs with the warning to leave his family alone and giving her one last chance for redemption. Karai next faces the Turtles during their attempt to retrieve a Foot artifact, an amulet called the Heart of Tengu. Despite her efforts, she is unsuccessful in stopping them.