Naruto/Avatar the Last Airbender Worlds Collide Book 2: Earth

Intro

Orochimaru was getting impatient for Sasuke's arrival. The Sound Ninja 4 had captured him, and even Kimimaro went to the battlefield to stop Naruto Uzumaki and his friend friends from bringing Sasuke back to the Leaf. So were was Sasuke? Kabuto Yakushi went out to investigate.

"Rasengan"
"Chidori"
It was a clash unlike anything Kabuto had ever seen before. Suddenly, Naruto Uzumaki and Sasuke Uchiha were gone.
"No. Damn it, no!" Kabuto said as he ran towards Orochimaru's base to tell him what had happened.

"Lord Orochimaru. It seems.... Sasuke and even Naruto Uzumaki has fallen into a new world!" Kabuto reported. Orochimaru growled in anger. Orochimaru looked at his arms.
"I have taken a new body.... might as well put these arms to good use." Orochimaru said as he walked to his library of forbidden jutsu.

It took a while, but Orochimaru found it. He killed a test subject, splattering his blood on the floor.
"Kabuto, prepare for transport. I would go myself, but there needs to be someone to keep an eye on the Leaf." Orochimaru said. Kabuto nodded.
"Demonic transport jutsu. I've done some research of this world... kill the Nine Tails brat, capture Sasuke, and find a way back... this jutsu as is now is a one way trip. Until you arrive back, offer your services to a man known as Fire Lord Ozai." Orochimaru said as the person's blood on the floor became a dark portal to the Avatar world.... leading to the Fire Nation!

"Intruder!" said a few Fire Nation soldiers before Kabuto smiled.
"Chakra Scalpel" Kabuto's hands turned blue as chakra covered his hands, turning them into scalpel like blades. Kabuto cut several tendons from the guards muscles, paralyzing them.
"Now I will have an audience with the Fire Lord, then I will return to heal you." Kabuto said smugly as he walked into the throne room of Fire Lord Ozai.

"Iroh is a traitor, and your brother Zuko is a failure. I have a task for you." Kabuto heard Ozai say to his daughter Azula. Kabuto smiled as a stream of information Orochimaru gathered about this world unsealed itself, causing Kabuto to learn all he needed to. Azula was a firebending prodigy, surely she could feel what he was about to do. Kabuto tested her by throwing senbon at points which would leave Azula temporarily paralyzed if it. Azula hadn't noticed. Kabuto sighed in disappointment.
"I'm sorry to interupt, Fire Lord Ozai. But she won't be able to defeat Naruto Uzumaki or Sasuke Uchiha without... assistance." Kabuto said and almost smiled smugly as Azula attempted to move.
"Who dares?" Azula asked before realizing that she couldn't move at all.
"I was sent on a one way trip here by Lord Orochimaru to destroy Naruto Uzumaki and capture Sasuke Uchiha, then find my way back to my world.... until then, Lord Orochimaru also told me to offer my services to the Fire Lord Ozai... I'm Kabuto Yakushi, of the Hidden Sound Village!" Kabuto replied.

The Naruto world:
"Soon Sasuke.... I will have you in my grasp again." Orochimaru said outloud.