Karai's Vendetta

"Karai's Vendetta" is the twenty-first episode of the 2012 TV series. It aired on Saturday, April 27, 2013.

Plot
In his lair, the Shredder asks the Kraang he captured why he and the others are after the turtles. At first, he doesn't understand it since it's out of its exoskeleton, but Karai points this out and they put it in the exoskeleton she stole from The Alien Agenda. When they put it in the exoskeleton, it refuses to answer, but it begrudgendly tells him the turtles are protecting April, whom they need for their plan. The Shredder takes an interest in this and tells Karai she must find April and being her to them in order to bring out the turtles.

Down in the sewers, April is training with Splinter and the turtles. The focus goes to Raph and Mikey when Mikey flips Raph after a direct attack. Mikey celebrates briefly, but Raph grabs him from behind, demanding him to give up. Mikey complies, only for Splinter to step in and teach them a lesson. He has Raph grab him from behind like he did with Mikey, but instead of surrendering, he licks Raph's faces. Obviuosly disgusted by this, Raph lets him go and is easily defeated.

Just when Leo, Mikey and Raph are watching "Space Heroes", Donnie comes in, talking about the results of a test he and April completed. He says that the Kraang have put some form of mutagen in the water, which is extremely dangerous. Mikey accidentally knocks the container of Kraang water on April, but it doesn't have an effect on her. She shrugs this off and goes up to the surface. Donnie tells the others that they can destroy an underwater Kraang base with a new invention he made. However, it runs on kenetic energy, which means the turtles have to supply it with pedeling. As they approach the Kraang's base, they encounter a creature Donnie assumes is from Demension X. They outsmart it and successfully break into the base.

Meanwhile, April meets Karai who has supplied herself with the alias, "Harmony" in Mirakami's noodle shop. At first, Karai keeps up the facade, asking April a bunch of personal questions. She decides to reveal herself when April almost tries her order: turtle soup. April tries to leave, but Karai grabs her and tells her that she's coming with her. Thanks to Mirakami, though, she escapes. She steals a pizza delivery guy's motorized bike, but is pursued by Karai on her motorcycle.

Just as the turtles prepare to attack the Kraang, April calls Donnie. She tells him Karai is chasing her, which causes him to panic. He and his brothers defeat the Kraang, but he tries to get the others to leave so they can help April. Leo is able to convince him to destroy the tanks instead of rushing to April's rescue. He rigs a Kraang gun to go off in 90 seconds, but the creature from earlier breaks into the room and attacks the turtles. Mikey defeats it and the turtles escape before the base explodes. However, the creature thought the sub was a female and latches onto it, but the turtles use explosives to force it to release them.

Back in the city, 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. 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 her deceased mother, which distracts her long enough to throw her down the subway stairs and escape.

The turtles and April all meet up in the sewers where April tells them about her fight with Karai. They're all impressed, but Splinter grows concerned and tells her that  since now both the Kraang and the Foot are after April, she's going to have to stay with them in the sewers, since it is the only place she will be safe. This results in April protesting and Donnie briefly cheering. At first, she's upset she won't see any of her friends and family for a while, but Leo reassures her that everything will go back to normal once the Kraang and Shredder are defeated and her father is rescued. Apirl thought for a while and soon she was  eager to get started on her training.

Trivia

 * This marks the end of new episodes on Total Turtle Takeover Friday.
 * Karai and April meet and fight in this episode.
 * In this episode, April reveals she lost her mother.
 * This implies Karai also lost her mother.
 * The sea monster in this episode is strongly based off the legendary "Loch Ness Monster"
 * The scene where Shredder and the captured Kraang having difficulty talking to each other is loosely base on their 80's counterparts.
 * This is the first time April used her weapon Splinter gave her in Baxter's Gambit
 * Donny introduces a new invention: A submarine powered by bicycles.
 * Karai's line that her father "is in kitchen utensils" was likely a reference to the 1987 series, where in the first encounter between Shredder and the Turtles, Raphael replied to the Shredder introducing himself by calling him "a kitchen utensil"
 * Karai's "Turtle Soup" line is loosely based off the well known Shredder quote "Tonight, I dine on Turtle Soup." from past Ninja Turtles incarnations.
 * April knows how to ride a motorcycle.
 * April's caller ID for Donnie is "Donny Boy". It should also be noted that flowers and stars surround his picture as well as a bow or butterfly on his mask and a silhouette of a cat.
 * This is the first episode with Karai where Leo did not fight nor talked to her
 * When the Turtle Sub goes into stealth mode, the lighting makes the turtles look like they all have red bandanas, which was their look in the original Mirage Comics.
 * Miwa means "beautiful harmony", which is the alias name of Karai. This alludes that Karai may actually be Hamato Miwa, Hamato Yoshi's/Splinter's daughter.
 * This is the second time we hear Karai speak Japanese.
 * Apparently, April learned Japanese from the turtles.

Video
promo video clip - http://geek-news.mtv.com/2013/04/24/tmnt-april-battles-karai-clip/