Disclaimer: I don't own Naruto or Harry Potter.

Pairing: Not yet decided, but there's a post Sasuke x Naruto. Vote for it, and it'll be YAOI/SLASH!

Full summary: Starts in the Valley of End. Using Sasuke's betrayal to cover his own, Naruto leaves Konoha to serve Lord Voldemort. In England, he enters Hogwarts, fifth year, and gets to know the people there. What will the fate hold to our beloved Kyubi-vessel?

Warnings: Expect anything.

Rating: M

Else: HP-crossover. Harry and they will be in their sixth year. And yes, I know that foxes and snakes are natural enemies, and you'll later find out the reason behind Naruto's siding with Voldemort.

Starts with the too-familiar scene in the valley of end. Naruto facing Sasuke!

THE ULTIMATE BETRAYAL

PROLOGUE

The Valley of End…beginning of everything

What I felt towards you, was wrong. However, it's what I still feel, you know.

Rain. Always when something bad happened, it also rained. The grey sky and the cold wind…it was like a regular thing. Naruto chased after Sasuke for quite a while before finally catching up to him at a waterfall's edge.

"Sasuke!" he yelled.

Sasuke calmly turned around to reveal his Curse Seal altered left eye. "Hey, dobe. Is it you this time? Going to stop me?" He said, ignoring the memories. The memories of that soft skin, those pink lips and the silky locks. But ex-lover or not, Sasuke will kill Naruto! He wanted the Mangekyou, and nothing will stop him! And so he smiled. He smiled through the pain that was slowly killing him in his heart.

Calmly Sasuke looked at his past lover. Memorizing those features, for the coming years. Maybe one day, after he had avenged his clan, they'd be together again.

What was between us…it had a meaning…I still love you, you know.

But there was something off with the picture. To his surprise, instead of the crestfallen face, Naruto was smirking at him. At the same moment, the Uchiha prodigy noticed few other, changed things in the blond. One of them was that the blond wasn't wearing his orange suit, but plain black pants and a black jacket. Naruto was standing, seemingly relaxed, but Sasuke knew him enough to know, that he was prepared for anything.

"You're leaving then. Well, it was about time" Naruto said. Sasuke raised an eyebrow, wondering if the other was bluffing.

"What does any of this have to do with you?" The Uchiha asked.

"Nothing. People think that we're very good friends. And no, I'm not here to stop you" The blond said, and his smile widened, when he saw the confusion in Sasuke's eyes.

"Then why are you here?"

I still love you, but I'm an avenger, you know.

"To perfect the plan I have been executing for six long years. To the world, Uzumaki Naruto was killed by the traitor Uchiha Sasuke, and his name will be carved into the Stone, while the Uchiha will be hunted for the betrayal." Sasuke's eyes widened.

"You…are you too leaving Konoha?" He gasped. Naruto smirked.

"Yes, I am. Everyone will think that I died. That you killed me. In truth, I'll be just leaving to serve my own master"

"Your own…master?" Sasuke gaped at the blond in front of him. This person in front of him, was the true Naruto? How couldn't he see this before? How was he so blind?

"Yes. My master, The Dark Lord Voldemort." To Sasuke's surprise, instead of starting to form seals, Naruto took from his pocket a stick of wood, and pointed it on him.

Did you ever love me? Did I matter to you?

"For I am the abandoned son of the Yondaime Hokage himself! I am the vessel of the greatest demon, Kyubi! I am the one born in light, and given to darkness! And so…I embraced it, welcomed it…"

"But…I don't understand!" Sasuke exclaimed "What about your dream? Don't you want to become the Rokudaime Hokage?"

"All I ever asked was love, but even you never gave me that! And so I stopped wanting it, turning my love into something else. Something you know so well!"

"Hatred."

I love you, I tell you! I love you like I can love nothing else! Why can't you see?

"Yes. Hatred." Naruto agreed, and stepped closer, raising his hand, so the stick pointed at Sasuke.

"Stupefy!"

And to Uchiha Sasuke's utmost shock he felt himself being stunned. Naruto walked calmly to him, and pointed the wand at his forehead.

"The art of the ultimate betrayal, Sasuke. You cannot outsmart a cunning fox" The blond said "Now, to perfect my plan, I'm going to erase your memory, replacing it with images of us fighting, and you killing me."

Has the fox inside you blinded you?

Sasuke's eyes widened. Naruto kneeled down next to him, looking deep down into the dark eyes.

"Sasuke…we could have been friends. We both serve masters, who have special bonds to snakes. Both are powerful, but my master is stronger. My lord Voldemort is so feared, that the people in England don't even dare to call him by his name. Compared to him, Orochimaru is nothing. You were a good lad, Sasuke, and I completely understand your reasons. But what was between you and me is over." The blond took a small object, a portkey, from his pocket, still pointing at Sasuke with his wand.

"Farewell and good luck in killing Itachi. Obliviate!"

I love you. Even if I don't remember your name, I'll remember you.
As the love I feel towards you, is as true as the earth and skies.

Don't forget me. I'll come for you one day.

Jus wait and see.

a/n: The prologue is short. I know, but it's only a brief explanation of what happened, so don't write in your reviews that the prolo was short. I know it. Thanks, and review.