Disclaimer: Naruto - Chainsaw Man - I own neither
Story Start!

"It... wasn't suppose to end this way... that attack wasn't... suppose to kill you."

It was a complete accident, but Uzumaki Naruto had broken his promise to himself, to Sasuke, to Sakura, to bring Sasuke back home. The hole that was ripped through Sasuke's side, caused by a Rasengan that had stricken a weakened Sasuke who lacked the chakra to form a chidori and guard against it properly. Sasuke's corpse was on the destroyed ruins of the Valley of the End.

Sasuke had survived the clashing of Sasuke's Indra's Arrow and his own attack in the sky, and when they crashed down on the ruined lands they fought in, they kept fighting... and then he had used a Rasengan. It was in the heat of the moment, and he expected Sasuke to counter with a chidori or dodge it.

No, Sasuke HAD formed a chidori, but it had fizzled out.

"It was an accident, something that happened in the heat of the moment." Kurama inside of him tried to help him, but Naruto stared down at Sasuke's corpse on the ground. With Sasuke dead, the Genjutsu keeping the Tailed Beasts trapped would be undone, and he could already heard the Tailed Beasts all breaking out of their prisons. The Kurama that had originally been inside of him was unsealed and landed on the ground, and the 8 other Tailed Beasts landed around him with ground shaking thuds one after another.

Naruto didn't look at any of them right away, instead he only stared down at Sasuke, his friend, and his blood that was spilled across the ground.

"I know... even though I didn't mean to do it, I still did it."

"HAHAHAHAHA! The Uchiha brat is dead!"

"Shukaku... shut up." Matatabi hissed at Shukaku, because the murder loving tanuki was horrible at reading the room. Even though Sasuke had trapped them all in an illusion and sealed them in stone, it wasn't like he had done it out of a personal hatred of them. None of them held any personal hard feelings towards him for that action, they were more mad at him stealing their powers to use against Naruto.

Naruto was devastated by what he had done.

They needed to be silent for him.

"Naruto, undo the Infinite Tsukuyomi with his eye. You can take it and implant it into Kakashi." Kurama, the outside Kurama and not the one inside of him, spoke with his loud voice, but managed to keep it gentle in tone. "You can decide what do you after that is done. You have to take care of business first." Kurama didn't want to disturb Naruto in his moment of mourning. As much as he personally believed this was the best outcome for everyone, Sasuke dead and Naruto alive, he knew that Naruto would never see it that way.

No amount of comfort, or sweet words, would ever make Naruto see this as the good ending, only a bad ending that he survived through.

Naruto took a deep breath, before he reached down and pulled Sasuke's Rinnegan out of his head.

With a jump, Naruto went over 400 feet through the air and landed on the cliff that was overlooking the Valley of the End he was in. He was at the edge of the Land of Fire right now, so he needed cross part of the Land of Sound, Land of Hot Water, the Land of Frost, and halfway through the Land of Lightning, in order to reach where Kakashi currently was, next to the Shinju remains. He would be passing through several countries worth of land.

Kurama placed his giant hands together and molded a sign.

Kurama, of his own willpower, sealed himself back into Naruto and recombined with the Kurama that was currently inside of him. Naruto felt that small surge of chakra, but didn't comment on it. He looked at the other Tailed Beasts, who watched him silently. He looked down at the ground, and he thought about what he wanted to say to them.

"Go where you want to go, you're all free now, I'm sure the other nations won't try and make Jinchuriki with you again." Naruto nodded to them, before he started to run. He was exhausted, but even exhausted he was still fast. His body was sore, aching, but it still only took him seconds to pass through the Land of Sound.

It started to get colder as passed through the Land of Hot Water and got into the Land of Frost, but he didn't care. He had a lot of thinking to do, but he could do that after the ultimate genjutsu over the world was released. Naruto saw giant vines going all over the world and keeping the entire population or humans and animals across the globe trapped in that illusion. No matter what his personal thoughts on what happened were, he needed to get that solved first.

His brain was dulled by the time he reached Kakashi.

The fact that Naruto returned alone was proof enough for Kakashi that something had happened, and he didn't mention it. He saw the Rinnegan in Naruto's hand, and he closed his eyes in a moment of mourning of his own.

"It... was an accident... I used a Rasengan, but he was out of chakra... his chidori..."

"I understand, and she will understand too." Kakashi placed his hand on the sleeping Sakura, who had been knocked out by Sasuke's genjutsu earlier, to prevent her from getting involved in the fight at all. Kakashi stood up and approached Naruto. Even several countries away, he had felt the sheer intensity of their battle. Their battle had changed the landscape around them to the point that he could feel it and see it from even this vast distance.

It was only the Shinju's roots that had kept the people of the world safe from their fighting, and prevented the mass extinction of their people. It was a battle that they could have only had under these conditions.

Naruto formed the handsign needed.

He kept holding Sasuke's Rinnegan in his hand when he did it, and quickly all of the vines keeping the people trapped came undone. Not just that, but many people were waking from their dreams. He was holding Sasuke's Rinnegan, so he could pass his chakra through it and undo the illusion that way.

"Just holding his Rinnegan like this... I know how it works. Maybe it's my connection to Sasuke, or maybe it's my Six Paths Sage Mode letting me understand it. I want you to have Sasuke's Rinnegan, use it to protect people when I'm done." Naruto stated as he held out Sasuke's Rinnegan. With Kurama remerging inside of him, he had plenty of chakra with work with now, even though he had been exhausted moments before.

The Infinite Tsukuyomi had been undone.

"You're going to leave." Kakashi stated after he witnessed what appeared.

A black portal.

A rift in space and time that could lead to another dimension altogether, he hadn't known Sasuke's Rinnegan was capable of such a thing. Even if the Rinnegan was implanted into him, he would never have the chakra needed to actually use that ability himself. Yet, Naruto could open a portal easily, whenever he wanted if he had that power.

"I didn't do anything wrong, and you don't have to tell anyone I'm gone. Tell them... you can tell them all that Sasuke and I both died. I don't care what you tell them... this is my own self-inflicted punishment. I killed Sasuke. I used a Rasengan on him when he was too weak to counter me. I know nobody else will ever punish me for this... but this is what I want to do for myself." Naruto explained to Kakashi.

Everyone was starting to realize what was going on, so he needed to go through the portal quickly before anyone saw him. Naruto looked at Kakashi for approval, to see if he was doing the right thing.

Kakashi looked down.

"Do what you need to do, I'll take care of things on this side. One day, I'll send people to bring you back, I promise." Kakashi ended it with that statement.

Naruto nodded, and he ran through the portal.

"Naruto-kun!"

"Wha?" Kakashi was confused when somebody screamed out his name in horror the second he passed through the portal by himself, and just as the portal started to close, a second person passed through it. It happened in the blink of an eye, and he was too exhausted to get a good look at who passed through it.

-On the Other Side-

"Was this the right move?"

Faster than anything else, Naruto sped through the new world he found himself in. The portal he passed through was already long gone, and he found life in this world around him. There were buildings and humans all over the place. None of them would be able to see him, he was moving too fast, but he was able to see them.

"This was your choice, and you made it. You have me, and the other Tailed Beasts chakra in you. You won't be by yourself, and you wouldn't be you if you weren't so foolishly hard on yourself." Kurama lamented Naruto's idiot nature at times.

Not this time.

Naruto was the strongest.

If Naruto didn't hold himself to the highest standard possible, then he could become corrupted by his own power just as Kaguya had. Naruto had killed his best friend, and that could have been a dark turning point for him. Naruto deciding to punish himself and reflect on what happened was a sign that he was still the good person at heart that he always should be. If Naruto had justified Sasuke's dead and decided he didn't need to be bothered by it, then there was a chance that Naruto could easily justify killing the next person that stood in his way.

Naruto avoided the dark path and decided to keep living as a good person.

Naruto removed himself from his people.

Naruto didn't want to be surrounded by thousands of people who would tell him "you did the right thing" or "he deserved to die" and let the people color his views of what he had done. He wasn't even planning on leaving his world forever, just until he had settled his internal feelings. He was just as much punishing himself, as he was protecting himself and others from justifying an evil act.

If you could justify the act of killing your best friend, then it wouldn't be hard to justify killing a lover, or destroying a village that threatened peace.

If Naruto could kill Sasuke and just say "I did the right thing" and move on, then that could spell the beginnig of a dark change.

Yet, Naruto said "I did the right thing, but it was wrong for me to do it" was how he felt.

With Sasuke dead, there was nobody that could stop him if he went down Sasuke's path.

Naruto was far enough away from where the portal had been, that even if somebody had followed him through it, they wouldn't be able to find him right away. Naruto gave a small, dark smile to himself at the thought of that. He rubbed the side of his head.

"I wonder if the people of this world need my strength, or if I should just blend in." Naruto laughed to himself at the thought.

Naruto fell backwards and landed in the grass.

He was so tired.

Chapter End!
Please Leave Me Lots of Nice Long Reviews, But No Flames Please!

1. In the Naruto vs Sasuke fight, there was a moment where Sasuke ran out of chakra for a chidori... and Naruto tripped over a rock after making a Rasengan. Well, in this story, Naruto had landed one step to the right, and didn't trip over the rock.
Remember, sometimes being 1 step to the right can change the course of history.