-oh i meant the war would happened after the japanese left when the gate was closed. After all, humans tend to move forward in industrilization while elves stick close to their nature. If somehow their idiology clashed against eachother in the future they will start a war.

-well nothing stops them from fully doing it. Remember Japan diesn't have the authority to controll what the magic academy can do. And they don't actually owned any of the kingdoms other then being watchers, if they'll make a fuss over it then politivall tensions will rise and japan will end up losing controll of the SR to UN. Also they have shown how devastating a human magic has done. Now imagine what the elves are capable of with their magic abilities.

Its interesting to see that lelei combined both magic physics and our physics in the anime (and manga of course)