Quote:Not necessarily.
... law and order and government by non-superpowered people exists only at the sufference of the demigods who stride the earth fighting their private little battles and pursuing their personal goals
Martial artists are not invulnerable. A little cyanide in the tap water would kill off most of Nerima easily enough, and that is not the most potent poison available, nor is that the only option.
Any attempt to take over, or even merely destroy, mundane society would pit the 'demigods' against the collective intelligence and technological might of the other 6 billion people on the planet, hardly a knockover. The scientific community is considerably smarter than any individual, and modern technology in many ways rivals the ancient gods for sheer power.
I won't say the martial artists couldn't win; I will say it would not be trivial - and afterwards, what would they do with their victory?
Exercising actual control over anything beyond their immediate area runs into formidable organisational challenges, but if they don't do so people in the area beyond their control will find a way to bring them down.
Simply reducing the mundane world to ruins would be easier than siezing control, but afterwards they'd die, when food production collapsed.
(Also, if mortals start acting like gods, the real gods tend to get violently annoyed, where they exist.)
If the martial artists didn't suffer the mundane world, abiding by its rule in most respects, the long term consequences would be at least as disasterous for them as for everyone else.
Even if they weren't, it would be of no consequence, because martial artists are human, part of a larger society. Here, in the real world, the US army could easily depose Bush tomorrow, and crush all opposition. Democracy exists only on the army's sufferance, technically.
In practice, the chances of that happening are too small to be worth considering, just as are the chances of a direct confrontation between the martial artists and the state.
I agree that the formal zoning Necratoid suggests is unlikely, but an unspoken convention whereby the martial artists police themselves is perfectly plausible.
Similarly, Jadeite was challenging the Sailors, not the martial artists. Interfering in someone else's challenge is just not done.
Anyway both parties are known to use magic in combat, not martial artists, which puts the fight outside Ranma's narrow range of interests.
Other crossover conflicts can be similarly explained. The multiple Oriochi are all different avatars of a greater god. Arkanphel predates the silver millenium by a few million years, long enough that all trace of his origin story could reasonably be overlooked. Chaos has been hiding its champions from one another until now.
Setting up the situation at the start of Hybrid Theory, with multiple godlings on a collision course, is certainly the kind of thing Chaos would like to do, especially if it's an avatar of the Crawling Chaos (who, like the inserts, may come from outside everything - may, since it's also possible that all Chris and Aaron's memories of the real world are fake).
Of course, a sufficiently baroque and powerful conspiracy can explain anything, which normally makes it a bad explanation, but not as bad an explanation as Last Tuesday-ism.
(Incidentally, the hybrid world contains at least one time travel device. If someone tried to travel to before the story started, what would they find? Another internal contradiction, or something as real as their present?)
From our outside perspective we can see that Last Tuesday-ism is the real explanation, but from inside I'd expect the characters, especially the more paranoid villains, to plump for conspiracy.
For one-universe crossovers in general, as opposed to those within a multiverse, the stories will fly as long as they don't require implausible levels of conspiracy to explain - not difficult, so long as the core premises of the shows don't directly clash.
I do like Hybrid Theory though.