[dirtyroboto]

WWI (World war 1) UK and JP are friends. The Uk Navy trains and sells ships to JP. The Brit Consulate is the closest (and still is) consulate to the Imperial Palace.
WWII (you guessed it) Japan moved into India (Britains slave whore) so Britain and Japan had some nose punching to do.
Most of the nose punching came from Japan and as taught by Britain (a small island nation) you don't give up, keep on fighting and even when you see a stiff upper lip, you should punch it good and proper.
Britain did not like this.
In an attempt to hold on to it's fortune (India) it sacrificed many of it's people to battle a far more determined people.
Thus you will hear a great many tale of why Brits hate Japs.
But in truth, the two island nations shared a great dream of world domination, and this is why, still to this day, both nations admire eachother with love and hate in equal measure.

Plus The Japanese REALLY love the Union Jack!