Author's Notes: I've been watching the New Toon recently, specifically season 4 when Leo becomes dark and more hot-headed. Warning! This fic features a rather dark and depressed Leo and is set at the beginning of the season, probably after Dragon's Rising (ep 10). The italic quotes are Karai's exact lines taken from S3E26 Exodus part 2, which I borrowed for the purpose of the story.

Rated PG-13 for some swearing and violence. This fic isn't beta-read so if you see any grammar/spelling mistakes, feel free to point them out to me, thanks!

Disclaimer: I do not own the Teenage Mutant Ninja Turtles or any related characters. I do not own the TMNT 2003 series.

Enjoy!

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Failure by sai ninja

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I crouch in the shadows watching them move past me, watching them run stealthily across the rooftop before I strike.

The cold air whips around my ears as I come out of my hiding place and pounce on my first opponent. I can almost see the look of surprise behind his mask and the soft muffled groan that escapes his lips as my blade slices through him. Slowly pulling my katana oiut, I barely notice him slide to the ground as three other Foot ninja appear behind me.

They attack as one and I immediately kill two. My katana flash in the night as they twist around me, parrying and slicing through the enemy, who all fall at my feet. I'm rewarded with a punch to the face and use the momentum to back-flip out of the way, effectively kicking my attacker in the chest, knocking him down.

Within seconds he's replaced.

I feel two other behind me, but have no time to think about them as I block yet another attack, crossing my swords before me. I swiftly knock the ninja's feet from under him and before he even realises he's fallen down, my blade slashes across his neck.

"That's for Master Splinter," I hiss, crouching low and sensing a surprise attack behind me.

Before I react, I'm suddenly knocked out of the way by another black clad figure, causing one of my swords to clatter to the ground. I roll out of the way swiftly picking myself up again, panting hard. I realise the element of surprise is no longer on my side, they're drawing closer to me like moths to a flame, circling me in with every step, confident in their superior numbers.

They've managed to corner me to the edge of the roof.

Rage suddenly takes over, almost tunneling my vision as I yell at my opponents before charging again. No need to be subtle anymore, I've got their attention, I've got them exactly where I wanted them and now I can make them pay.

I jump up high before they strike at me and kick one of the ninjas in the face before landing without a sound. I whip around and immediately chaos ensues as ninja after ninja attack and I parry. The blades hiss in the dead of the night as another Foot ninja falls, but not before slicing my leg just above the knee. I flinch, but keep my mouth shut, shifting my weight to my other leg and striking even harder at the opponent behind me.

Another one bites the dust as Mikey likes to say.

I've lost count long ago of how many have fallen.

"That's for Mikey's legs," I snarl at the figure before me, viciously plunging my flat blade through his ribs and enjoying the sight of his blood pooling out of the wound.

I quickly clear another circle around me, finally beginning to install some fear in the anonymous ninja around me. I spot my second katana and make a beeline to it, twisting and turning as I continue to lash out at them. Catching the hilt of my sword with my foot, I kick it up in the air and catch it, feeling whole once more with both my weapons. They are forever a part of me, steel extensions of my arms that clash with metal and cut through flesh.

Another suddenly lunges at me and I swiftly kick him in the gut, causing him to stumble into another. Caught off guard, my blades are quick to slash at their chests.

"That's for Donny's arm."

Looking over my shoulder, I breathe hard as I note their wave of attacks start to dwindle. I smile to myself as another drops beneath my katana and I notice their confidence turn to fear and precaution. But I have no mercy for them and I show no mercy as I counter attack, landing a kick at the first ninja in sight and cutting the one beside him through the shoulder. I sprint past another and enjoy hearing his soft grunt as my blade plunges into his thigh as my foot kicks him in the face.

"And that's for Raph," I growl over his body, before pulling out my katana still stuck in his leg. I swing it over my shoulder and continue my massacre, ignoring the aches and cuts covering my body as the Foot come at me tirelessly, hoping to defeat me before I cut them to pieces.

I won't let them.

They defeated me once, but never again. Besides, it's not them I want. It's not across their throats I want to draw the blade of my katana.

Suddenly, I feel a hand grab the hilt of my sword tightly and pull it to one side. Caught off balance, I feel my arm betray me as my steel blade is turned against me, drawing nearer to my side as several ninja overpower me. I kick and punch in retaliation, using my free hand to slash at the bodies around me. The sight of seeing my own blade used to harm me again causes a wave of anger and madness to abruptly envelop me. Twisting my own body around, I use my shell to crunch my attacker's arm and grunt in my effort to pull away from him in time to parry another's attack. I can hear the ninja screaming in pain behind me and glance over my shoulder, watching him cradle his shattered arm before swinging my swords around, bringing them down on his neck.

"And that, Karai, is for stabbing me through with my own fucking katana," I yell, kicking at the ground, jumping high in the air before another sword strikes at my side. I land away from the group of ninja, once again cornered by the rooftop and wait.

Laughing softly, I watch standing weapons at the ready as I feel them hesitate. They still circle me, however the bodies of their fallen comrades have started forming a wide barrier between us.

"What's wrong?" I jeer at them, feeling their cold eyes on me. "Too scared of a turtle?"

They don't answer. They never do. But I know my words affect them as I notice them begin to feel restless again.

However, suddenly and without a sound, they retreat.

I feel my hands ache as I grip more katanas even more tightly in response. They can't leave, I haven't finished, I'm not done, and yet I watch them run away silently in the opposite direction, stopping only at the edge of the roof before disappearing into the darkness.

Blinded by rage, I quickly sheathe my swords and begin to follow them, jumping from rooftop to rooftop in my thirst for vengeance.

I slow down as I reach the end of my pursuit. The Foot Ninja are before me, facing me like statues in the night, weapons at the ready and waiting.

I freeze to a halt as I realise they're waiting for orders.

"Karai," I spit out angrily, my voice low and fierce.

I sense her before I can see her. My trained eyes spot her standing above her clan on a higher rooftop, partially hidden in the shadows.

She's the reason I'm out here tonight. She's the reason I'm out here in the darkness, fighting every night. She betrayed me. I thought she had honour, but my family almost died because of her deceit.

For weeks after our final battle with the Shredder her words rang out in my mind every time I closed my eyes.

"You are too kind, Leonardo. Much too kind."

They've kept me awake for the past month. And everytime it reminds me of my failure. My failure to protect my family – to protect my brothers. She blinded me with her tricks and now I'm here to make her pay.

"KARAI!" I shout out this time, gritting my teeth and slowly drawing my blades out again, ready for anything.

"You are making a mistake, Leonardo," she tells me, stepping out of the shadows; sword in hand.

I barely take any notice of her words, eager to attack as soon as she is close enough. Ready to slice her throat.

"You will pay for all the ninja you have killed," she continued, jumping down from her tower and advancing towards me, "with your life!"

She pounces, but I'm ready for her. Our katana clash and before we separate again, I can feel her foot connect with my already-wounded leg. My knee buckles with a crunch, but I barely notice as I jump back only to attack again. I leap over her, hoping to strike by surprise, but her swords anticipate my movement once more.

We have the same weapons, we learnt the same techniques and we both aim for the kill.

She comes at me again, but I parry her attack, catching her off guard as my left blade slashes her thigh. She flinches, but recovers almost instantly and with a cry, she doubles her effort to overwhelm me with multiple attacks.

My knee protests in the effort, but I won't let it stop me. Not now, not after everything, not when I'm so close to revenge. Not when I can already see my blades drawing blood from her neck.

I land a solid kick to her gut, causing her to fall backwards. In an instant, my katana strike down at her chest, but she rolls out of the way, swiping my feet from under me. My head hits the concrete roof hard and a katana falls from my hand. For a moment, I'm disorientated, my eyes become unfocused and I lose track of the enemy.

My first and possibly last mistake.

Taking advantage of my weakness, her foot kicks my second weapon out of my hand. I try to jump out of the way, but my knee betrays me and I find myself lying helplessly as the tip of her katana suddenly shines before me.

"Grave mistake," she taunts me as if I were her student. "All your efforts to find me have weakened you over the past month and now you shall pay for your foolishness."

Her blade pushes into my side of my neck, but I refuse to turn my head away, my eyes burning into hers.

"What are you waiting for, Karai?" I manage to spit out through ragged breaths. "If I'm such a failure, why don't you kill me already?"

The defiance in my tone surprises her and for a brief moment, I can almost see pity in her eyes.

"Defeat is not your style, Leonardo. I am surprised that you should give yourself so easily to death, but since you seem so sure -"

She pulls her blade away from my throat only to aim it better at my chest.

"Goodbye, Leonardo."

I keep my eyes open, watching a mixture of emotions on her face as she lifts her weapon, ready to plunge it into my heart.

She strikes quickly aiming for my heart and I ready myself for the cold steel to plunge through my plastron. A shadow suddenly races towards me out of the corner of my eye and before the tip of the katana reaches my chest, I hear the distinct clink of metal upon metal.

Karai looks just as surprised as a sai traps her blade, forcing it out of her hand, before the dark figure barrels into her. In one fluid movement, my brother has pounced on her, locked her body under his and holds his weapon at her throat.

"Why don't ya tell your flunkies to retreat before I slice your pretty neck," he growls, looking over his shoulder towards the army of Foot ninja ready to attack.

I watch her narrow her eyes at him, but eventually obey. "Foot ninja. Retreat."

"Good girl," he tells her, holstering his sai back in his belt and prying her other katana out of her hand. "I should probably kill ya right here for what you were about to do, but unlike you, I have more honor than that."

Pushing himself off her, he picks up her blades and promptly throws them over the rooftop into the dark alleyway underneath.

"Now go," he tells her and in an instant she's up on her feet and onto the roof ledge.

"One day, Leonardo," she hisses at me before disappearing into the night, "you will pay."

I watch silently as Raph turns towards me as soon as she's gone, collecting my katana on the way. In one quick movement, my arm's around his shoulders and he helps me up to my feet, half carrying me as I limp on my bad leg.

We move as quickly as we can, Raph carrying me on his back as he uses the fire escape to climb down to street level. As soon as we reach the dark alleyway, he leaves me leaning against the brick wall as he opens the nearest manhole and then helps me climb down.

He remains silent the whole time, his eyes avoiding mine as much as possible and his posture stiff and tense. I know he's angry, I can tell by the sharp glint in his eye and the way his jaw is locked, but I don't care.

He doesn't understand – he never will.

Again he takes my arm and helps me walk along the sewer, steering me left and right as the darkness engulfs us more and more. Finally, we come across an open space to one side with a high-vaulted ceiling and I suddenly realise how far away we are from the Lair.

Raph isn't taking me home after all.

As the realisation hits me, I turn my head to face him, but instead he ducks under my arm and pushes me away.

I fall awkwardly, avoiding hitting my knee again and falling instead on my hands. I keep my head turned to one side, fixing the small opening to the far side of the room where the sewer waters all connect and disappear behind the wall.

I wait for him to speak first.

"Ya wanna tell me what the fuck you were doin' back there?" he asks, suddenly towering over me.

I let out a strangled laugh as I listen to him. Raphael about to lecture me and put me in my place after all the crap he pulled before. Sensei must be losing his mind to send him after me.

"I'm serious, Leo," he continues, his voice terse. "I can deal with you going dark an' moody and acting out like me, but I ain't dealin' with you suddenly going suicidal -"

"I'm not suicidal," I barely whisper, enough for him to hear me. Looking back up, I notice he's still standing above me, arms crossed over his chest.

"Oh really? Then what d'ya call going after the Foot like that every night fo' the past month?" he barks down, his eyes narrowing at me. "What d'ya call going into battle against a fuck load o' ninja by yourself and then confronting their fuckin' leader?"

I feel the anger start to boil within me again as his words beat down on me.

"And why the fuck did I find ya sitting on yo' ass, ready to be cut open by Karai?"

In a flash I'm up on my feet, katana in hand, and roughly pushing my brother back against the wall.

"Don't say her name to me!" I snarl, my face barely an inch from his nose.

"Or what?" he asks, sai already in his hands. "You gonna cut me up like those Foot ninja?"

I pull back, suddenly realising I'd like nothing more than to punch his face in and it scares me.

"This phase, or whatever it is ya going through," Raph continues, still gripping his weapons and frowning hard at me, "it's gotta stop, Leo. I know ya keep blaming yo'self for what happened with Shredder, but it wasn't yo' fault, you hear me."

But I'm not listening. It was my fault and no matter what my brother thinks or tells me, it won't change anything. I prefer to give in to the anger within, letting it blind me completely, rather than try to make him understand.

"And what the hell do you know about anything?" My voice is cold and dangerous. Unconsciously, my arms are already outstreched, katana in hand. My body shifting into an offensive stance.

The mood darkens immediately and Raph's face turns to stone.

"Don't push it, Leo."

Grunting loudly, I launch myself at him, striking hard and fast. He blocks each and every attack until he lands a solid kick to my chest. I fly back into the wall, my sheel cracking behind me, but I'm not ready to give up, not ever – not until he understands.

"You just don't get it, do you?" I yell at him, charging at him again and managing to punch him with the hilt of my sword. "You can't stop me, I have to do this. Someone has to get revenge for what they did to us."

Raph barely blocks the next katana strike before I swipe his feet underneath him.

"And it has to be me!"

My fist connects with his jaw, but he catches my arm as I stricke and swiftly kicks me in the side, before rolling away.

Putting some distance between us, Raph remains crouched as his eyes study me calmly.

"Why?"

"Because I'm the leader," I shout back, lunging furisouly at him with both katana. "I'm the one that failed you. I should have known about Karai, I should have seen it coming."

He evades every one of my attacks, striking in return, and it angers me even more. I try to grasp him – hurt him- but the anger only makes me careless and sloppy. Suddenly, the heel of his foot hits the side of my head and stumbling backwards, I begin to feel warm blood trickling down my face.

"I failed all of you," I finally admit, my voice becoming desperate and wild, reflecting my emotions inside and betraying my calm exterior. "Mikey, Don, you – Master Splinter! Can't you see what I've been trying to do this past month, can't you seen that I'm trying to make it up to you?"

Drawing ragged breaths, I watch the dark expression on his face turn to confusion.

"No one asked ya to."

"But you don't need to," I tell him, my fists clenching again. "I already know, all right, I know I made a mistake. I already know I'm a failure!"

I charge again in a final effort to hurt him, to make him hurt as much as I do inside. I hear myself yell in anger and pain as my katana reach him, but he beats me back down again and this time, I don't get up.

I can't bear for him to see me so weak.

"Ya not a failure, Leo," I hear him speak up behind me. "You trusted Karai an' she hurt you – bad. I get it. But that don't make you a failure, bro, that only makes you – human, I guess."

My eyes snap open in surprise and fix his face.

"And seein' you beat up yourself about your mistakes, training harder than before, seein' you care so fuckin' much, well... now I'm starting to realise why Splinter made you leader."

Listening to his words, I feel my gut start to clench. Using the back of my hand, I brush away the moist from my eyes and expecting to see blood, I'm surprised when it comes away wet instead.

"But going after the Foot," Raph continues, crouching down beside me, his hand on my shoulder, "going after Karai by yourself, that's taking it too far, bro. You need to let go, you need to forget and most importantly you need to forgive yourself – because we already have."

His words hit me as if he'd just doused me with a bucket of ice-cold water, washing away the deep sense of failure that had enveloped me for the past month and sparking the hurt and fear inside. I look up at him through frozen tears and for the first time, I notice the worry and concern in my brother's eyes.

"Raph, I don't know how," I tell him with brutal honesty, my voice suddenly cracking. "I'm... I'm such a mess."

I try to grasp for air, but close my eyes instead, letting the tears fall down my face. My muscles suddenly ache all over as I drop my katana to the ground, my fists clenching at the damp ground instead as a month's worth of bottled up emotions start pouring out of me.

"S'okay, Leo," I hear Raph behind me, still clenching my shoulder. "We're here for you, big brother, we're all here for you no matter what."

And as I lay there giving into the pain and tears, with Raph crouching silently by my side, letting me cry but not letting me go, I hear the words play through my mind – the same damn words that have haunted me constantly every single night.

"This is not what I wanted, Leonardo, this is not what I wanted."

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