Debuting in the show's second season, Karai eventually became one of the series' main recurring characters. A woman torn between honor and family, she appears both as an ally and enemy to the Ninja Turtles, a dichotomy that plays a part in most of her appearances. Her allegiance varied throughout the series: first being an anti-hero (or anti-villain) during seasons 2-3, then villain in seasons 4 and 5 and finally became heroic near the end of season 5 and in later episodes.
An alternative version of Karai (voiced by Karen Neill) is a major character in the 2003 Teenage Mutant Ninja Turtles animated series by 4Kids Entertainment and Mirage Studios. The supervising producer Lloyd Goldfine envisioned the cartoon Karai as having a "sleek, no-nonsense, commanding, Japanese accent. "The original comics' (and Karai's) co-creator and the show's consultant Peter Laird agreed, but emphasized that she is also "a powerful and dynamic individual". Laird opposed to having "all kinds of goofy, ludicrous weapons systems built into Karai's new Shredder armor." He was also "disappointed" to see Karai at April and Casey's wedding and fighting on the side of the "good guys" in the end. Regarding Karai being called "Leo's girlfriend" by the time of the show's third season, Laird noted that "contrary to what some TMNT fans might fantasize, Turtles don't mate/have love affairs with humans."
As a child, Karai was found and adopted by Ch'rell, the Utrom Shredder, after her parents abandoned her at a young age (in the original comics, Karai had no relation to him). He took her in and raised her as his own, teaching her ninjutsu. An aspiring practitioner of Bushido, she became his most trusted follower, even trusted to his true identity as Ch'rell and told her that the Utroms were savagely hunting him. When the Utroms fled for New York, Karai remained in charge of the Japanese Foot Clan. Karai first appears as one of the highest-ranking members of the Foot Clan, similar in status to Hun (who holds a grudge against her); eventually, she becomes the clan's leader. Throughout the series, she appears both as an ally and enemy to the Turtles, sharing a complicated relationship with Leonardo. Karai was the only Foot member who knew that the Shredder was really an Utrom other than the Foot Mystics. After Ch'rell's exile at the end of Season 3, Karai spent all of Season 4 and Season 5 trying to make the Turtles pay for this. When she appeared as a guest of April and Casey's wedding, her vendetta with the Turtles was confirmed to be over.
Karai made her animated debut in Season 2, in the series' loose adaptation of the Mirage Comics' "City at War" story arc. When the Purple Dragons, the Mafia, and the Foot were fighting for control of New York City after the Shredder's reported demise, Karai arrived in the city after hearing the news of the gang war taking place and quickly enlisted the aid of the Turtles to stop it, promising an end to the Foot’s vendetta against them in exchange for their assistance. Leonardo, believing that Karai was honorable despite her legacy, convinced Donatello and Michelangelo to aid her. Raphael initially refused, although he later recanted. Together, Karai and the Turtles eventually retook control of the New York Foot and consequently its underworld. However, the end of the story, it was revealed that Karai had been manipulating the Turtles (much to her dismay), and had been working with the not-dead Shredder all along. However, she showed sadness when the Shredder (Ch'rell) vowed to get revenge on the Turtles after she had made a truce with them. In a homage scene, the way Karai held Leonardo hostage is exactly how the Shredder held him in the first live-action film to force the other three to surrender.
Karai and the Foot reappeared in Rogue in the House, Part 1, where a fully-healed Ch'rell retook control of the Foot. As his first order of business, he deployed a killer robot (disguised as Splinter) to eliminate the turtles. Realizing that their agreement with the Foot had been recanted, the turtles decided to face the Foot again in their temporary HQ—a ship stationed at the docks. Leonardo, Raphael, and Splinter were taken hostage during their encounter, and Karai was forced to fight Leonardo. Despite Leonardo’s lack of resistance, she proved unwilling to kill him.
Karai’s internal conflict—her loyalty to the Turtles as fellow Bushido-practitioners vs. her loyalty to her father—was the main thrust of her Season 3 storyline, as she was pulled from both directions to take a side during their various encounters, even working together with the Turtles at times. She also appears in a cameo in Japan. Karai managed to stay in the graces of both sides until the Turtles faced the Shredder again in the season’s finale. As the Turtles were chasing Ch'rell, Karai tried to reason with Leonardo, pleading him to let her father leave. When Leonardo refused to let Shredder go, Karai fought alongside with her father and (unintentionally) accidentally stabbed Leonardo in the shoulder with his own sword, damaging his carapace, although she later prevented the Utrom Shredder from killing the Turtles while they were unconscious. Despite her efforts, however, in the end, the Shredder was taken prisoner and exiled by the Utroms, while Karai and the young Foot Tech Division Head Dr. Chaplin are also captured and sent back to Earth and placed in a prison. Before disappearing with Dr. Chaplin, Karai cried out to Leonardo: "This is not what I wanted!"
With her father gone and dead in the eyes of the world, Karai took over the Foot as well as the mantle of the Shredder (in a deleted scene she even says that Karai "no longer exists", completely replaced by The Shredder) sometime after she and Dr. Chaplin got out of prison. This new Shredder "would retain the traditional iconic elements, but have a different treatment". Furious at what she saw as a betrayal by the Turtles, Karai plotted 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 believed successful. She later once again duels Leonardo (who was not at the lair at the time of the assault), who defeated her but then departed with the warning to leave his family alone and giving her one last chance for redemption.
Karai next faced the Turtles during their attempt to retrieve a Foot artifact, an amulet called the Heart of Tengu. Despite her efforts, she was unsuccessful in stopping them.
Unknown to the Turtles or Agent Bishop who initially charged them with retrieving the artifact, the Heart of Tengu was a mystical artifact that allowed the Foot to control its Elemental Mystics, who were in reality the heralds for a man-demon that had centuries ago terrorized Japan as The Shredder. The destruction of the clammer unleashed a chain of events that resulted in the demon Shredder’s resurrection. His first target was Karai, who had “usurped” the Shredder’s name. The Tengu Shredder and his heralds made their way to Foot HQ. Karai had the Foot prepared for this, having developed mystic-based technology to combat the supernatural, but despite her efforts and those of the Turtles, who believed her the key to stopping him, the Shredder bested Karai in battle, seriously injuring her. Karai was rescued by the Turtles and taken back to April O'Neil's apartment, where she was tended to. Dr. Chaplin followed her trail, and was brought to her after being caught snooping around the building. Karai heals and, recognizing the threat the demon Shredder posed and her inability to stop it by herself, Karai agreed to a "temporary" alliance with her enemies. It was soon learned that because she shared The Shredder's mantle, Karai had the latent psychic ability to lower Shredder's defenses through a shared link. This was accomplished by absorbing the majority of the Demon Shredder's power into herself, a power that she presumably keeps. This gave the Turtles an advantage in their final conflict with the demon. Karai helped pave the way for her namesake's destruction, and Dr. Chaplin helped the Turtles co-ordinate their battles against the demon. After the battle, Karai, touched by Chaplin's devotion to her, promised him that she was going to worry more about the immediate future, and they departed the battlefield hand-in-hand. It is possible that after it she forgot her grudge against the Turtles and resolved their difficulties off-camera considering what happened in later episodes.
Karai is not involved in any main storylines in the Season 6 in which the Turtles and Splinter travel a hundred years into the future. Karai appeared in one episode of the Fast Forward television series, in The Journal. The TMNT found a book said to be written by Casey Jones and April O'Neil, detailing what occurred following the Turtles' return to the present from the year 2105.
According to the journal, Leonardo was invited for further training with the Ninja Tribunal, and was surprised to find that Karai was doing the same. After some time, Leonardo declared - based on his knowledge from the journal - that someone would betray the Tribunal, and given their history, he suspected Karai. He later spied on Karai and, witnessing her talking to The Shredder's helmet, believed his suspicions confirmed. Leonardo attacked Karai, but it was revealed that she had brought the helmet for a ritual where she would cast off Oroku Saki's influence forever. The Tribunal noted that Leonardo has fulfilled his own prophecy - that he was the traitor - and was exiled from the training grounds. As the events in this book were written by Splinter and Cody to discourage the Turtles from knowing too much of their future, it is unlikely anything of the sort occurred (or will occur).
Back To The Sewer
Karai next appeared in the season finale, Wedding Bells and Bytes, having been invited to attend the wedding of April O'Neil and Casey Jones. It appeared as if she and the Turtles had resolved their difficulties off-camera, and she arrived at the ceremony with Doctor Chaplin by her side. She and Chaplin later assisted the Turtles in fending off the sudden onslaught of the Cyber Shredder and The Foot Clan. Though she had no lines, it was apparent that she had moved on with her life and was no longer involved with the Foot.
Karai also makes an appearance in the 2009 animated film Turtles Forever, in which Karai freed Ch'rell from the clutches of the 1988 Shredder, Krang, Bebop, and Rocksteady, and aided the Utrom Shredder in modifying the Technodrome with Utrom technology. The Utrom Shredder, consumed with rage for revenge on the Turtles, wanted to destroy every dimension where Ninja Turtles exists, even though such an action would most likely destroy himself. Karai began to have doubts about the whole affair and secretly intervened rescuing the classic Turtles, '88 Shredder, Krang, and 2003 Splinter as the Utrom Shredder was prepared to destroy both the 1988 and 2003 Turtles. In the end, at the Turtles Prime dimension, (Mirage Turtles) Karai fought alongside the Mirage, 1988, and 2003 Turtles as well as the 1988 Shredder and Krang and 2003 Splinter, to stop the Shredder from destroying Turtles Prime. In the end, after Ch'rell was defeated, she commented that the Shredder would always return.
A major plot arc that started with her character during Season 2 of the show was that she was loyal to her father, despite his dishonorable ways. After Ch'rell's exile at the end of Season 3, Karai spent all of Season 4 and Season 5 hating the Turtles and possibly after season 5 making a truce the with Turtles. When she appeared in 'Wedding Bells and Bytes' as a guest of April & Casey's wedding, it was assumed that her vendetta with the Turtles was over, but Turtles Forever (if it is meant to fully correspond with the 2003 series' plot line) indicates that with Ch'rell's return, her loyalty to him does not exceed her truce with the Turtles. But during Turtles Forever, she finally betrayed The Utrom Shredder and became a friend of Turtles once again.
She has appeared in 25 episodes & 1 movie:
- City at War, Part 1
- City at War, Part 2
- City at War, Part 3
- Rogue in the House, Part 1
- Rogue in the House, Part 2
- Space Invaders, Part 2
- New Blood
- Mission of Gravity
- Hun on the Run
- Exodus, Part 1
- Exodus, Part 2
- Bad Day
- Still Nobody
- Scion of the Shredder
- Prodigal Son
- Good Genes, Part 1
- Good Genes, Part 2
- New World Order, Part 1
- New World Order, Part 2
- Past and Present
- Enter the Dragons, Part 1
- Enter the Dragons, Part 2
- The Journal
- Something Wicked
- Wedding Bells and Bytes
- Turtles Forever