Re: Naruto 642
The only necessarily plausible excuse I can think of happens to be the Law of Conservation of Energy in the Universe.
Now, to start off, chakra blatantly does not obey this law. Yeah you can make the argument that turning physical energy into chakra is merely a transformation and not a creation but what the fuck is "spiritual energy" supposed to goddamn be in terms of physics? And then you have cases where chakra is transformed into matter and then you have a case of mass-energy conversions going fuckin screwy. On some level, the molding of chakra violates the everloving shit out of that law, and that's ok because ninja magic and suspension of disbelief.
The point I'm seeing as a possible explanation (that I guarantee you isn't Kishi's line of thinking) is that natural energy is that energy in the universe that the Law applies to. As in it cannot be created, and it cannot be destroyed.
I am a leaf on the wind. Watch how I soar.