The Cosmos Is Vast.

I know that really goes without saying, but it is worth repeating. It isn't technically infinite, but it is quite big. The part that a self aware being, such as Toshi, can survive in is actually a fraction of a fraction of the total whole. That is just excluding the parts that don't have the same fundamental laws of physics that support his existence.

Of those parts, there are layers to everything. The layer that is of most importance to us right now is the layer that involves memetic energy. Metaphysics, to be specific. Like normal physics that is made up of things like quarks, electrons, disappointment, and photons, memetic energy can be broken down into fundamental building blocks as well. We call these monads. There are six in particular. Up and down are your most common. Think of them as the foundation of Mana. I won't bore you with the particulars, even if it is quite fascinating. What concerns us, and Toshi in particular, are the monads that make up a living, intelligent being. The four 'soul' monads, as they were. Specifically referred to as Demonic, Weird, Angelic and Top.

Yes, the human soul is made up of Top memes.

It's more a matter of energy, really. The human soul is made of the most energetic and resilient memetic particles. It takes the most energy to make one, and when you break it down, you can make any other monad from a Top monad. This is why demons and what not are always seeking out human souls. They are just so full of pure TASTE. However, monads don't work like quarks, even if there are similarities. They absorb and give off up and down monads, and reproduce and grow, then sometimes break off or 'shed'. That last part is what is important to us.

Toshi has been shedding Top monads like an english sheep dog right after a really soapy bath.

His very presence produces Top monads and they just drift off him. This is above and beyond his normal astronomical production of ordinary mana. He's basically shedding flakes of "soul". Everyone does this, but nobody notices. It is such a small amount for most souls, it really doesn't matter, but Toshi is ten BILLION souls in one body. When Toshi's soul gets dandruff, there isn't enough Selsun Blue in the GALAXY to get that shit under control.

Now what effect has this had? Well, remember how Toshi has a soul strength of 10, which is about ten billion souls? If someone has a soul strength of 1 they would have only the strength of one soul. Makes sense, right? Now, some of you have asked yourselves, "Hey. Can someone have LESS than a soul strength of one?" And the answer is:

Unfortunately, YES.

You see, if you don't have at least a soul strength of one, you really aren't... real. Which is to say, you exist. You resemble a human. You walk around like a human. You talk like a human. You do things like a human, but you don't have any free will. You are, in effect, an NPC. It's difficult to explain the particulars, and sort of pointless, so I'll stick to what matters for this discussion.

The vast majority of people on Reverse World are NPCs. NPCs, not being a full soul, are a DRAIN on the planet's mana supply. They require more mana than they produce, and are constantly leeching away the very health of the planet they exist on. If the mana supply dips below a certain point, these NPCs start draining mana from other sources and those other sources are what allows the very planet to function. Think of it like a power grid. You might have enough power for everyone, but sometimes have problems getting it to where it is needed. This leads to the occasional 'black out' in an area. Now what happens when you have a mana black out?

Existence Failure.

Now, it doesn't happen all at once. No no no. It's a proton here, an electron there. It is very spread out, but it isn't insignificant. The planet was losing TONS of material in spurts all over the place on a weekly basis. If you were to measure the circumference of Reverse World and compare it to Toshi's original world, Reverse World is twelve miles LESS. That's right, the whole world has been shrinking away. As mass disappeared, the planet has been settling, getting smaller and smaller.

If you compare the history of the two, Mirror world has had WAY more earthquakes, volcano eruptions, and general geological nonsense. If it ever reached a certain tipping point, the planet's crust would lose integrity and whole land masses would break apart before sinking into the mantle. The entire planet would become a churning ball of magma as it dwindled away, like someone pulled the plug on a multi-dimensional bathtub.

TOTAL Existence Failure.

Well, it WAS in danger of doing that, but not anymore.

Not since Toshi arrived.

Toshi isn't just pumping out mana, but those "soul flakes" he's shedding are glomming onto anyone nearby. The number of NPCs becoming full blown PCs has shot up through the roof in Tokyo. Not only that, but if Toshi focuses on someone in particular, emotionally speaking, they are likely to get more... err... flakes.

Yeah, I'm sure you figured out what's up with Naora.

This was thought to be a good thing. More real people means less strain on the system and more free mana to gather up. It's not like it's DANGEROUS or anything! You see, Reverse World is still damn close to the dark matter reefs, so any human learning magic is RIGHT OUT. Yup. Magic is not possible in mirror world. God and all his angels checked. They are quite sure of this. No magic at all. Period. End of statement.

You could have a soul strength of, say, 6 and it wouldn't matter. You couldn't DO anything with it. So it was perfectly fine that Naora's soul strength had been climbing astronomically in comparison to everyone else on the planet. It didn't matter WHO had a strong soul, as long as the soul was strong and pumping out free mana. Everything was A-OK.

Nothing To Worry About.

...

...

Unless...

The angels and God in their arrogance forgot about one of the most fundamental of magics. The first magic that develops on any world, really. Magic that focuses on the internal workings of one's body.

Aura manipulation

Magic works best when there is uncertainty. The less you can observe magic, the more uncertainty it has. Aura manipulation isn't flashy and only works internally, which makes it the least observable magic. So if you study hard, practice, work out rituals and patterns, if you learn how to do martial arts without needing to think about it, if you train your body to the point it moves on its own without being observed even by the mind of the one performing the martial art.

You see where I'm going?

Now this doesn't mean that you can start doing Crouching Tiger, Hidden Dragon bullshit just because you got a strong soul. While it was always possible to perform aura manipulation, up until Toshi's arrival, nobody had been strong enough to actually take advantage of this little loop hole. Even if you were, you needed to be amazingly good at martial arts, and not just something you worked out in a self-defense course. It had to be something ancient, with the weight of history to give it meaning. Given the extreme outlier conditions needed, it was little wonder that, as far as God and his angels were concerned, magic was just not possible on Reverse World.

Then a magic detector in heaven went off as Naora bisected a punching bag with her bare fist.

And That Was The Precise Moment God's First Angel Did The Metaphysical Equivalent Of Shit Himself.