According to Google Maps, if you could fly like a bird across the North pole, you'd fly about 8146.740 kilometers from Japan to Great Britain.
The great britain by far
Great Britain
far
france, great britain, japan
They had a treaty with great Britain
China
France, Italy and russia were sided with Great Britain in WW1
Like Great Britain, Japan is an ISLAND NATION (surrounded by water).
Japan wasn't in WW1.
I would not think Manga would be popular in Great Britain because Manga orginated from Japan.
According to http://www.freemaptools.com/how-far-is-it-between-great-britain-and-ethiopia.htm it is 3985 miles or 6413km.
Well great Britain could of made a peace treaty.