[Episode starts with Leo narrating the events of what happened that day after the Earth is saved and the Triceratons are completely extinguished.]
Leo: [narrating] It's been weeks since we saved Earth and stopped the Black Hole Generator. Things have finally been cooling down. No more Triceratons. No more Kraang. And best of all, no more Shredder and his goons. They've completely disappeared from the city. So tonight, the night of the full moon, Master Splinter is performing a very special initiation.
[We cut to the lair. April is now wearing a black jumpsuit and headband.]
Splinter: April O'Neil [Japanese] This tanto represents the Dragon: Strong, fierce, intelligent. A dragon not only relies on its physical strength, but it's keen intellect as well. Be at one in spirit and body. Be like the dragon. [speaking Japanese.]
April: Hai sensei.
Splinter: April O'Neil, you are now a Kunoichi of the Hamato Clan.
Donnie: All right!
Raph: Yeah! [laughs.]
Mikey: All right! Oh, yeah, celebration time!
Raph: Congrats, April.
Leo: You deserve it.
Donnie: You did great.
April: Thanks, guys! You're the best!
[She hugs Donnie. Donnie gets happy, puts his hands on his heart, all grab April and throw her up to the air.]
[Theme song]
[We cut to the turtles and April on the rooftops after the celebration.]
April: Oh, man, remember when I had a hard time keeping up with you guys? Can't believe I'm finally a full-fledged ninja.
Raph: Sure, you made it to the third dan, but there's still seven more grades, each with different levels, so...
Donnie: Don't rain on her ninja parade, Raph. It's amazing you made it to Kunoichi, April. Ignore everything Raph just said.
Mikey: Yeah, I always do. Makes life way simpler.
Leo: Come on, ninjas. Let's call it a night.
Mikey: Let go!
[They continue on. However, April had a feeling that they're being watched.]
Leo: City's quiet. For now.
Raph: I'm sure that'll change soon. With Shredder gone, there's gonna be a ton of gangsters and super villains moving in on his turf.
Donnie: You okay, April? What's wrong?
April: I'm pretty certain someone is following us.
[They looked and saw a black cat.]
Leo: What?
Mikey: Aww, look at you! Coochie woochie woochie!
[The cat disappears as mist forms.]
Donnie: Okay, this is weird.
Mikey: Um, hello?
[Laughter echoed as a figure of a woman reveals herself. She has a slender body with long black hair, a black body suit and wore a witch hat.]
Shinigami: Let's play a game. Give me one of your weapons or I'll take April something precious your shells.
Raph: All right, sister, play time's over.
[He tries to attack but he gets kicked back.]
Shini: My name is Shinigami. Do you know what my name means?
[They begin to attack and Leo knocks her hat off. She’s got golden eyes, black eyeshadow, purple lipstick and an attractive face.]
Shini: [offended] I can't believe you'd hit a lady. So you really are real, living, breathing Kappa. So cute.
[Mikey started to fall in love with her.]
Mikey: You ain't so bad yourself.
[She wrapped her chain around knocking Raph and Leo before she kicked him.]
Shini: My sensei doesn't need a Turtle weapon. Your tessen will do just fine.
April: You're gonna have to get it from me, witch.
[April begins to attack Shini. She summoned out her blades and began to attack. April steps back and saw that her sword is gone.]
Shini: A dragon tanto? You must have just become a Kunoichi. This will do nicely. [speaking Japanese.]
[She disappears into a red mist.]
Raph: I can't believe that crazy girl took us to school on a Sunday!
Leo: She just threw us off. Now we know her tricks.
Mikey: I don't know, she was pretty awesome.
April: Yeah, awesome.
[Later, the Turtles and April returned home, reporting Splinter about the new enemy.]
April: I mean, getting my butt kicked the night I become a Kunoichi. It's like the whole universe is saying it's not meant to be.
Splinter: That is not the universe speaking. That is the self-doubt of April O'Neil speaking.
Leo: I've been there, April. Doubting everything, it's poison. Believe in yourself.
April: I just feel like a failure.
Splinter: There is no such thing as failure until you give up. That is when you fail.
April: Thank you, both.
Splinter: You must uncover the identity and allegiance of this new assassin. Claiming your weapon as a prize, that is an initiation into a ninja clan. Be warned. It seems this new assassin may be working for the Shredder.
[in the lab, Donnie had been researching about the Shinigami.]
Donnie: Hmm, I'm not coming up with anyone called Shinigami in any of the international crime databases.
Leo: You got anything at all, Donnie?
Donnie: Well, the Shinigami are powerful gods in Japanese myth that bring death and destruction.
Raph: So we got something in common.
Mikey: This girl is super cute, guys. Maybe we could turn her to the light side.
Leo: We gotta find her first. Let's split up and see if we can track her. Maybe we can draw her out.
[They take the party wagon.]
Leo: No sign of any activity. Got anything, Donnie?
[Donnie is on Channel 6.]
Donnie: Still searching. Nothing so far. Got anything, Raph?
[Raph's in the shellrasier.]
Raph: I got nada. Streets are clean. What do you got, Mikey?
[Donnie is on a cargo, eating pizza.]
Mikey: Mmm. I got pizza. Mmm, mmm. What about you, April? April?
April: Leo, I just spotted Shinigami. I had a weird vibe that something was happening at Shredder's old lair.
Leo: Shredder's back? But the lair was abandoned.
April: Not anymore. Call the rest of the guys.
Leo: Don't do anything until we get there.
April: Thanks for the vote of confidence.
[April looks inside the old church and saw someone on the throne.]
April: Is that Shredder?
[When the figure stands up...but to our shock and complete surprise. It is revealed that the figure turns out to be none other than...Karai?!)
April: Karai.
Shini: Karai, I bring you the red-haired girl's tanto blade.
Karai: So Splinter finally made April a Kunoichi? Kind of a shock.
Shini: Yes, she seems so frail and clumsy when you first look at her. Like a silly red bird
[April arrives.]
April: Well, this Kunoichi tracked your butt down, Karai. What're you doing, anyway?
Karai: None of your business. Just go.
[The turtles arrive.]
Leo: We'd like to know what's going on here too.
Karai: Leo, calm down. The brain worm that was controlling me is gone. I'm not your enemy.
Raph: Oh? So then why did your crazy friend attack us?
Karai: It was only a test to see her skills. Shinigami's an old friend from Japan. She was never gonna hurt you.
Shini: At least not permanently.
April: She's telling the truth. That brain worm thing is gone. They're not after us. They're after-
Donnie: Shredder.
Raph: So what's up with the headgear, Princess? Daddy issues?
Karai: I wanna rebuild the Foot. Bring back honor to a clan that Shredder poisoned for almost two decades. And when I finish, I'll destroy Oroku Saki and his empire once and for all.
Mikey: Life isn't about revenge, sis. Come back to the lair with us. Master Splinter would love to see you.
Karai: No. I have to carve out my own destiny.
Donnie: Fine, we're leaving.
[They begin to leave but April isn't going anywhere.]
April: First, I want my tanto back. Now.
Karai: If you want it back, take it from her. I mean, shouldn't be hard for a Kunoichi, right?
April: Fine by me. I wanted a rematch anyway.
[Shini slides down and started to take out the tanto. Then, the two girls began to battle. As the battle between April and Shinigami continues, April's anger is amplified by her gift from the Aeons, causing her to begin attacking with psychic blasts, but Shinigami soon manages to overpower and incapacitate her.]
Donnie: I'm stopping this ri-
Raph: Let her fight her own battles.
[April began to use her powers but Shini dodged. She started to leap and then punch her down.]
Shini: Little red bird. [chuckles.]
Karai: All right, that's enough, Shini. Give her the tanto back.
[Shini does so. April, still full of rage and fury, tries to get the tanto sword off, but Donnie stops.]
Donnie: [calming her down] Easy, April. Don't let that weirdo get to you. Calm down.
Mikey: Come on, this place is lame anyway. We're going to an awesome place. The sewers! Booyakasha.
[Shini mimics as they leave. In the lair, Leo told Splinter about Karai and Shini and how they are trying to end the Foot Clan.]
Leo: Not only that, she's taken over Shredder's old lair. She's even wearing a version of his helmet.
Splinter: This is most disconcerting, but her choices are her own. April? What troubles you?
April: I think I'm pretty much ready to revoke the Kunoichi title, Sensei. Maybe I need more training.
Splinter: Come. Perhaps it is time I taught you an advanced move called The Dragon's Tail.
April: I'll try anything.
Mikey: Dudes, you know what time it is, right? Time for some Chris Bradford. Boy!
[Chris is seen swimming.]
Chris: I'm coming for you, Destroyo, and nothing's gonna stop me.
Destroyo: Ha, accept my killer dolphins trained to eat human flesh. Good-bye, Chris Bradford. Killer flesh.
[Dolphins begin to attack.]
Chris: Killer dolphins? Time to power up with Chris Bradford's Roundhouse Kick Hyper Drink.
[Chris drinks it and punches the dolphins one by one. and kicked Destroyo.]
Chris: Chris Bradford's Roundhouse Kick Hyper Drink drink it!
[Meanwhile, Tiger Claw, and his minions have been searching for Karai. Karai and Shini are entering a weapon store.]
Fishface: Is she still one of us, Tiger Claw?
Tiger Claw: No. The brain worm is gone.
Fishface: A martial arts store? What is she, shopping for nunchucks?
Rahzar: It's a front. We store tons of illegal weapons in the back.
Tiger Claw: She is here to raid us. The little cub has claws.
[Karai and Shini enter the store and the lights close.]
Tiger Claw: Foolish child, I can still see in the dark.
Rahzar: So can I.
Fishface: I cannot, so this is kind of upsetting.
Karai: Tell your master I'm taking the city back, Tiger Claw. Piece by piece.
Razhar: Where'd she go?
[Fishface gets dragged and Razhar goes after him. Tiger Claw aimed his blaster to find Shini.]
Shini: Here kitty, kitty, kitty.
Tiger Claw: What's this?
[She begins to use a hypno spell and attacks Tiger Claw. She disappears in red smoke and attacks, Tiger Claw kicks her.]
Shini: I have claws too!
[She begins to attack until she gets thrusted into the air and collapses.]
Rahzar: I like you, Karai. Let me finish you quick. Tiger Claw won't make things so easy for you.
Karai: Whatever, Bradford. I plan on taking you all down.
Tiger Claw: Karai!
Karai: No, Shini!
Tiger Claw: Surrender. Now.
Karai: You win, Tiger Claw.
[She drops the katana.]
[In the lair, Leo picks up his phone.]
Leo: It's a text from Karai. And it's just one word: "Help."
[Everyone gasped. Karai and Shini are restrained and hanging.]
Fishface: So now that we have them, what should we do with them?
Rahzar: I vote eat them. You can never go wrong with eating them.
Tiger Claw: No! We wait for their friends. Karai called the Turtles minutes ago.
Karai: You knew all along?
Tiger Claw: Do you take me for a fool? There is no help for you.
[He breaks her phone.]
Karai: Where is Shredder? Where is that coward hiding?
Fishface: You do not get to make demands, girl.
Karai: Oh, no.
[She used her knife and got free.]
Fishface: Ay caramba.
Tiger Claw: Clever girl. But cleverness only gets you so far.
[He charges at Tiger Claw]
Rahzar: Take that brat down, Tiger Claw.
[She dodged as she fought him. He clawed her and then grabbed her arm.]
Tiger Claw: I always thought you were a spoiled, petulant child. This world will not mourn you when you are gone.
Mikey: Tiger Claw!
[Ninja stars stuck him, releasing Karai. Tiger Claw roars in pain.]
Karai: Always have to wait till the last minute, guys?
Leo: Tiger Claw, I thought you and Shredder left town. You know, after we defeated you and all.
Tiger Claw: We will never leave until you and Splinter are put to rest.
Leo: Team, take 'em down.
[They charge. Shini looks up as Mikey frees her and helps fight the mutants.]
Mikey: Got you, Rahzar.
Shini: Let's play "walk the dog"!
Mikey: Whoa, that's exactly what I was gonna say. We're, like, so similar, Shinigami.
[They both get dragged by the werewolf.]
April: Back off, Fishface.
Fishface: Ah, yes. Call me what you will. I am the most interesting fish in the world.
[Donnie glares with flames appearing on his head as Fishface lets her go.]
Raph: You're running low on nine lives, Tiger Claw.
[Karai used her snake arms and pulled Tiger Claw away from Leo. Tiger Claw pulls her off.]
Tiger Claw: You are beaten. Your shell will hang in our new lair as a trophy.
April: I don't think so.
[April used a blind power and kicked him in the groin a second time.]
Donnie: Wow, The Dragon Tail. Right in the fur patch.
Mikey: Booyakasha!
[They disappear.]
Rahzar: I hate it when they do that.
Fishface: Eh? Um, we are in trouble.
Tiger Claw: Run! Oh, no.
[The weapon shop explodes as we cut back to the lair.]
Karai: April. Shini and I want to apologize. Sorry about earlier.
Splinter: Miwa.
Karai: Father.
Splinter: Do not take on this burden of fighting the Shredder alone. Ally yourself with your family. Let us help you.
Karai: I've grown up, Father. I need to rectify all the wrong deeds Shredder has done my own way.
Splinter: You are just seeking vengeance. This anger you carry was inherited from Oroku Saki, not from me.
Karai: I know. Don't worry, Father. I'll make you proud of me. Soon.
Splinter: I am already proud of you, my daughter. April. You have proven yourself a true Kunoichi. I always knew you had the Dragon Spirit, and apparently the Dragon's Tail as well.
April: It's all thanks to you, Sensei.
Raph: So what now? We know Shredder's still out there.
Leo: I have a bad feeling things are about to take a turn for the worse.
[Somewhere in the woods, there is a mansion. Defeated and humiliated, Tiger Claw comes and speaks with the Shredder, who is on a bed, naked and is wounded, recovering from injuries sustained by Splinter at the battle in Earth's Last Stand, is under the care of Baxter.]
Tiger Claw: I don't know if you can hear me, Master, but Karai she is trying to take control of the city, undo everything we have accomplished. She just destroyed our weapons cache, and I believe she's not going to stop there.
[Weakened, Shredder breathes heavily, Tiger Claw watches him in shock. Cut to Shredder, still breathing, then cut to his face as he closes his eyes and speaks.]
Shredder:[weakly.] If it is a war she wants,[Slowly scrunching his eyebrows.] then it is a war, she will GET.
[Stockfly hooking up an IV containing mutagen and injects it on Shredder. His eyes open wide, they are white and green, indicating that the mutagen is starting to take an effect... slowly. ending the episode.]