This is almost 100% some sort of bullshit, it sounds a bit too magical to be true.

"H2O is split into hydrogen and oxygen which react chemically to produce energy"

What? This is just bullshit x)

Firstly, you need energy to break bonds between atoms (the hydrogen and the oxygen). Them "reacting chemically" afterwards would not give you a net gain of energy, that's impossible.

And if you think it isn't, remember that if you could split water and recombine it to end up with more energy than you started off with, you do not only have a damn good car, you have endless amounts of energy. Unlimited power as Palpatine would say. A nice idea, but completely impossible.

Or perhaps it's just a regular car and the guy put petrol in his mout without swallowing it just like magicians do...

Suuuuuuuuure. And who puts those atoms back together to produce that water vapor?

If only there was a thing like video editing, then he wouldn't have had to drink gasoline.

Needs to be said that it's fully possible to create the hydrogen that the Mirai uses without dirty industries, it's just that it's a lot cheaper doing it the good ol' polluting way so that's the most used. But as you say, still a lot cleaner. And a lot more expencive as well ;P

The only real problem is that it's been invented in one of the most hated countries in the world.

So explain to me how its splitting hydrogen to use as fuel without a secondary energy source for the conversion. It doesn't make any sense.

Yes. Hydrogen produces roughly three times the amount of energy the gasoline does. And water is nothing but hydrogen and oxygen.