-Naruto-
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Naruto has a great idea!
So he was practicing with his awesome Transformation Jutsu (you can really get anywhere when you're transformed into a bug), and he thought "Why stop at one?". After all, if one Academy jutsu is so easy to improve and so useful when improved, why shouldn't Naruto try to improve another? Fuzzy had wholeheartedly agreed, so Naruto snuck into the library (which seriously needed better security) to get a scroll for the Clone Jutsu.
Naruto spent the day trying to get it down, but he just couldn't do it. The theory was ridiculously easy to understand, but it was just impossible to pull off! Fine, that doesn't really matter anyway. If Naruto gets how it works, he just needs to improve it. He doesn't need to do the regular version if he can make a better one!
All of Konoha shivered with a worrying sense of foreboding.
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-Kurama-
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Huh. It turns out that a jutsu actually can be too pathetic to do. Kurama didn't even realize that it was possible to use that little chakra.
"I suppose that if a human is pathetic enough, they'd need a pathetic jutsu to match. That's fine. You're right, you don't need to be able to do the jutsu if you can do an improved version. I would suggest trying to make it solid. Most clone jutsus use a medium to make solid clones. For example, the Earth Clone Jutsu infuses earth with chakra to make a functional, solid clone. But a medium isn't really necessary, it's only a way to conserve chakra. I have absolutely no medium, no physical body at all, but I am made of chakra so potent and dense that I have physical form. For someone like you, who has all of my chakra inside of you, making a clone that's a fraction of my size and power should be fairly simple."
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-Naruto-
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Naruto eagerly started experimenting with making his clones solid. His first thought was to try adding more chakra - Fuzzy said that he was solid because he was made of a lot of chakra, so clones would probably be the same!
Although the clones kept poofing away as soon as Naruto made them. He wasn't sure exactly what was wrong, but maybe just pumping them with a ton of chakra isn't enough? Maybe it was something about the original jutsu that meant you couldn't just shove them full of chakra and hope for the best.
So Naruto looked at his scroll for a little longer. He was getting a little frustrated by this point. There's nothing in this jutsu that would make it explode! Most jutsu just get stronger when you overload them, so what was he doing wrong?!
Wait a second. Most jutsu get stronger when they're overloaded, but the jutsus that Naruto is thinking about are jutsus like his Great Breakthrough, where the chakra is moving and dissipating. The clone jutsu is completely different. It's self-contained, and doesn't dissipate until you tell it to. The only thing holding it together is the chakra itself, but if you overloaded the chakra past its limits...
So you just have to improve its durability! Naruto's a genius!
The next few weeks were a lot of trial and error, but by the end of the month Konoha was swarmed by thousands of blond menaces, painting every surface he could find with a goofy smirking fox.
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A/N - I just want to be clear, this is not the Shadow Clone Jutsu. It's an improved version of the Academy Clone Jutsu. It is solid, but it doesn't have the extra memory transfer funtion that Shadow Clones have. It's more of an intermediate step until Naruto feels like messing with whatever archive the Shadow Clone Jutsu is hidden in (it can't only be written in that one scroll if it's so weirdly common, even if it's supposedly forbidden). That's why I called this chapter "Foreshadowing". Naruto's gonna create a ton of chaos with this clone jutsu, but just imagine how crazy it's gonna get when he gets actual Shadow Clones!