The 2012 animated series version of Karai is a rebellious member of the Foot Clan, a master kunoichi and the teenage (16-year-old) daughter of the Shredder. She is voiced by Kelly Hu. According to IGN, "while Karai does seem to be fairly loyal to Shredder, there's no doubt that she's at least somewhat open to walking the line with Leo and the others."
In "New Girl In Town", she and Leonardo have a similar relationship to that of Catwoman and Batman; as she tries tempting him to be more like her. While Leo wants her to see she's as not as bad as she appears. She confronts Leo, who is separate from his brothers. During their first battle, she blinds him before attacking him. However, she leaves him alive. She later runs into him again in an alley and fights him again. They both exchange some banter and some blows until Karai holds a sword against Leo's throat, trying to convince him that he's not as good as he appears. She also notes during her fight with Leonardo that while she understands the Shredder's revenge, but she's uninterested. And that she jokingly stated that he should get a hobby. She tells him to meet her a top of a building without giving him any more information other than she wants to show him something.
Karai meets with the Shredder, who is not happy that she let Leo live. She tries to lie and say that he escaped, but the Shredder doesn't believe her. He tells her that she must kill him or else. Their scene ends with Karai calling him "Father". Her relationship with her "father" may be somewhat abusive, as she intensely becomes frighten after making the Shredder angry at a comment.
At midnight, Leo meets Karai on top of the building she informed him about earlier. She tells him that they're there to steal a famous katana in a museum. Leo refuses to help her, which upsets her. Before she takes out her dagger, Leo stops her and tells her that he believes that there's good inside her. Raphael comes in, and is angry at him for "holding hands with the foot". Upon Snakeweed's attack, she stands there smiling until Leo asks for her help. She throws him a knife and leaves. Whether this was to help him or not is undetermined.
In The Alien Agenda, Karai finds the turtles fighting the Kraang. She becomes somewhat concerned over the Kraang When she tells the Shredder, she tries to convince him to take some concern over them due to the mutations that happened to the turtles, Xever and Chris Bradford, he believes that this is all nonsense, and ignores her. She'd become disappointed that Shredder has no interests or concern over the Kraang. Shredder then reminds his daughter his reason for his ongoing vendetta against Splinter. As he blames him for his disfigurement and then tells his daughter how Splinter hurt "us"; indicating that she believes Hamato Yoshi also wronged her. To find out more she questioned Leonardo when they next fought, during which she flirts with him. But he refused to tell her anything, and also said for her to leave his brothers alone. Raphael asks Leonardo about her, and if they should tell the other two brothers, but Leonardo said that she was going to leave them alone. Raphael thought that that was a stupid idea. She keeps it to a point, as she followed the 4 brothers into the Kraang lair, seemingly undetected. However, when the turtles realized Raph was missing, he had found Karai and pinned her down. The two fought, and while Raphael was a more worthy opponent for her, Leonardo broke them up. Leonardo argued that Karai was good, both Raphael and Karai said that she was evil, while Michelangelo and Donatello were perplexed by who she even was. The fight gathers the Kraang's attention who attempt to subdue them. Karai makes the fight worse by releasing the mutagen and unleashing a monster. She then takes a Kraang droid and brings it to her father as evidence. She also offers it as technology for Baxter Stockman to use against the battle against the turtles.
In Enemy of My Enemy Karai appears out of nowhere. She immediately pulls her blade and attacks Leo. Raph, Donnie, and Mikey all join in to fight her. She mentions that she overheard Donnie talking about the Kraang. At first they don't want to let her in on the situation but Raph lets slip that they are trying to stop a full-scale invasion.Suddenly, a flash of purple light comes from the T.C.R.I. building. A door opens in the side of the skyscraper and a strange craft floats out. It is resembles a jellyfish, with a round body, three short, stubby tentacles and a single purple "eye". It is piloted by two Kraang who spot the turtles and Karai and move in to attack. The ninja run across the rooftops, narrowly avoiding the ship's energy beam weapon. Karai ducks into an alley while the ship pursues the turtles. Leo runs out to draw the ship's fire while the other three make it to the sewers. Leo joins them and they watch the ship from a storm drain. The ship activates a cloaking device and vanishes to avoid detection by a passing Police helicopter. Karai returns to the Foot's headquarters and reports what she has seen to Shredder. He ignores the Kraang threat and tells her that they will soon recieve a shipment of new weapons to end their war with the turtles and Splinter.After a brief spar, she tells him that she wants to help them fight the Kraang. She is afraid that Shredder's stubborn refusal to see anything passed his revenge will get them all in trouble. She asks to work together but Leo refuses and leaves. spots them and opens fire. The ship chases the van down the street. Leo asks Mikey for an escape route and Mikey accidentally leads them into a dead end. The ship starts to blast through the Shell Raiser, when Karai appears on a motorcycle. She jumps it onto the Kraang ship and plunges her blade into its hull. Leo drives the Stealth Bike back to the others on the Shell Raiser and reveals that he brought Karai with him. Raph is less than thrilled but Leo tells him to hear her out. Karai tells them that they need her help and that the only way to take that ship down is with a missile launcher from the Foot shipment. Raph smells a trap so Karai says she will get the launcher herself. Leo agrees that if she gets the weapon, the turtles will team up with her to stop the ship. As Karai retrieves the missile launcher, she spots the turtles. She tackles the Shredder out of the way so that the grenade electrocutes the Foot Soldiers and the man with the diamond eye and fires the missile at the turtles. Leo makes it to the box of missile launchers but is confronted by Karai. She tells him that she feels betrayed and that he is just as short-sighted and obsessed as Shredder. She then reveals to Leo that Shredder is her father. Leo is shocked by this news. Karai says that the deal is off and attacks Leo. After a short fight the ship returns and Karai hides from it. When she emerges, she finds that Leo has already taken a missile launcher and gone after the ship. Meanwhile, the other three turtles fight a losing battle against Shredder. Leo takes aim and fires his missile at the ship. It crashes into the wharf, knocking Shredder into the water. Karai dives in after him while the turtles retreat. Karai helps the Shredder out of the water. He thanks her and tells her that he has found a pet for her and holds up a captured Kraang.
In "Karai's Vendetta", Shredder's interrogation of the captive Kraang proves futile, as it does nothing but senseless squealing. Karai suggests putting the Kraang into the limbless exo-suit they possess. Upon hearing it speaking relatively sensible English, the Kraang stated that they hunt the turtles because they protect April O'Neil, who is crucial to their plans. Thus, Shredder dispatches Karai to capture April to draw the turtles out. She meets her under the alias "Harmony". She then reveals her identity by trying to feed April turtle soup. April forced Karai to pursue her on foot, but she traps herself in an alley. She pulls out her weapon and Karai compliments on it before disarming her. April tries attacking her directly, but Karai dodges her attacks and starts attacking her, easily overpowering her. She knocks her into the street and demands to know why she's so important as she continues attacking her. April is able to defend herself and provide her own questions. However, just when Karai has her pinned, she mentions losing her mother, causing Karai to hesitate which distracts her long enough to throw her down the subway stairs and escape.
When Karai makes her first appearance in the episode New Girl in Town, airing February 1, 2013. She is described as a rebellious teenager and expert martial artist who stirs up trouble. "As lethal as she is beautiful, Karai brings a whole new level of chaos and complication for the Turtles," says the Nickelodeon description. Kelly Hu said: "I have to admit that I’ve never seen any other version of Karai, so I really have nothing to compare her to -- which is kind of a good thing, because then I just get to play her as I see her myself. But she’s sort of feisty, cunning and kicks butt. She gets to have a little going on with Leonardo. What I like about playing this character is she’s not all bad. She has a conscience that she has to wrestle with...But see, I don’t know about the other Karai's or story lines in other series, so I don’t know how it matches up, if it’s the same or different or what." Hu added that she "was pleasantly surprised at how edgy and cool she was -- and skinny!" Nickelodeon published early character design sketches of their interpretation of Karai on the Internet.
Karai is typically a bad girl type character. She revels in the freedom being in the foot clan gives him, and taking advantage of it at every turn. Still she operates on a more complex code than her clan or father, and seems to have a greater concern over the community around them than the Shredder. For example, she once tried to convince Leonardo to steal a precious katanna, and another left them to deal with a violent aberration mutant, yet she grows worried about the intentions of the Kraang and even attempts to aid the turtles in fighting them on one occasion. She is rather intolerant of the grudge her father has for Yamato Yoshi and the Turtles, paying around with the strange ninjas until they attempted to use a truce she made with them to assassinate her father.
She is shown to be taller than Leo (and April) Karai has black hair that is dyed blonde in the back, also two strands of her hair falls over her ears. She wears several black earrings, and red eyeliner on her brown eyes. Karai wear silver armor, black material worn under her armor, traditional Japanese shoes, and a purple belt with design on it. She does have a civilian outfit, with a punk esque design with worn jeans and a leather biker jacket with metal studs.
Karai's relationship with her father is complicated. She seems to fear the Shredder just like Bradford and Xever do and she obeys him, but she doesn't appear to respect him as much. It's possible that she wants him to respect her when she mentions the Kraang and shows him the droid she picked up. In Enemy of My Enemy, a little more insight is given to Karai's relationship with her "father". Twice in the episode does Karai save her father from getting zapped by a tazer ball and drowning. Shredder is not kari's dad spinter is, spliter's babby is kari.
Leonardo is the first of the Turtles that Karai meets. While she attacks and fights with him often, she never does him any serious harm and just enjoys sparring with a worthy opponent. Leonardo, in turn, is both confused by and attracted to Karai (as shown in "New Girl In Town"). She is dangerous, but Leo believes there's some good in her. She seems to be deceitful and manipulative in The Alien Agenda, using Leo's feelings for her against him, especially in his time of need.
In Enemy of My Enemy, she returns, seeking information on the Kraang from the turtles. This time, instead of wanting to fight the turtles, she decides to make a truce with the turtles in order to defeat the Kraang ship. She goes againsst the Shredder's orders because she knows they'll all die if they don't set aside their differences and take down the ship. At first, the turtles, mainly Leo, are very skeptical about her and decline her request for a truce, but after she leads it away from the Shellraiser, they comply. Because Leo saved her and allowed her to speak to all of Turtles, Karai develops some feelings of friendship for him. However, because he and his brothers tried to attack her father, the truce was called off and her feelings were hurt. Now she's vengeful towards the turtles and is willing to do whatever it takes to take them down. Whether or not her relationship will heal in future episodes is unknown.
Raphael is the second of the Turtles that Karai meets, and the first to find out about Leonardo's "friendship" with her. Unlike his brother, Raphael immediately distrusts her. Karai, meanwhile, seems to enjoy teasing Raphael due to his frustration which is easily set due to being insulted right away, which brings more amusement to her while fighting with him during battle. Raphael seems like a more worthy opponent for Karai in battle due to the fact he sees her as an enemy working for the Foot, but she sees him more as a play toy for her amusement.
April is the first and possibly only female human she's met. Based on their brief encounter, they seem to have a lot in common. They both know Japanese, know how to drive a motorized vehicle, they're kunoichis, are the romantic "interests" of one of turtles, and lost their mothers at some point in their lives. They later on became enemies in "Karai's Vendetta". However when april mentioned that she lost her mother and throw karai then the subway entrance and escapd, karai looked up with a guilt look on her face, this might suggest that they also may have a similar past. another interesting note is that whenever karai reported back to shredder, she might not have mentioned that she failed at capturing april.