Blanket Disclaimer: I don't own Naruto. If you thought I did, that's sad.
A/N: Ah, another side-story. This relates to Introspection - Chapter 9: Fight It's not too bad, but not great. sigh... maybe i should stop.
Story 3: Sasuke's Fear
During the battle in the Valley of the End, Sasuke witnessed the powers that Kyubi had over Naruto. True, one could say that Naruto still had some semblance of control over the Kyubi, but Sasuke thought otherwise. No one was there to experience the fight. Sasuke saw that although Naruto had more power and was wielding it, he was not in control. In fact, it looked as if the blond boy was possessed.
The second time Sasuke witnessed the possession, was during the battle with Kabuto and Orochimaru. Naruto transformed even more. Not only did he have the fangs and claws, he grew ears and tails. He looked like a hybrid fox, more-so a fox. After the battle, Kabuto and Orochimaru were dead. Naruto was still rampaging. Naruto only came too his senses when Sasuke directed a chidori through Naruto's shoulder. Sasuke had ended up in a coma for a week.
Sasuke hated having to resort to almost killing his friend again, but he remembered his promise to the blond. I promised him death and release if he were to loose control.
Sasuke never wanted to grant that wish. He thought that when Naruto merged with Kyubi, he would have full control of the powers and would never loose control. Naruto had, unfortunately, told him otherwise. In fact, after the merge, there is more of a chance that Naruto would loose control of the power since they were one and the same now.
Sasuke's worst fear was not death. Death was inevitable for a shinobi. He and Naruto had learned to accept death and fight willingly knowing that either could die in battle. Sasuke's worst fear was that he would have to keep his promise to Naruto. That he would be the one to have to kill his best friend and precious person. This promise was killing him from the inside. He wasn't sure he could do it. Not only will Itachi get what he wanted, but Sasuke would loose the only person who weighed so deeply in his soul.
Sasuke was afraid that he would be the cause for loosing Naruto. If he lost Naruto due to circumstances, he would be saddened, but he did not fear it. He did not want to be the one that caused the lost of his one true friend. The one time he lost Naruto when he left for Orochimaru was tough enough. Top it off with his new feelings for the blond was devastating.