What is “扶桑” (ふそう, Fusou) ?
“扶桑” (ふそう, Fusou) is another name for Japan from ancient times.
There was a Chinese legend that there was a huge tree called “扶桑木” (ふそうぼく, Fusou Boku) at the end of the east. “木” (ぼく, Boku) is a tree. Based on this, in ancient China, Japan was called “扶桑” (Fusou). The Japanese in those times also called their country “扶桑” (Fusou) or “扶桑国” (ふそうこく, Fusou Koku). “国” (こく, Koku) is a country. So it is not really strange for Japanese people if an imaginary country resembling Japan is called “扶桑” (Fusou) in a fictional world.
As per the “Kantai Collection (艦隊これくしょん, Kantai Korekushon)”, the name of the battleship “扶桑” (Fusou) is adopted from here. “扶桑” (Fusou) was the first dreadnought battleship built for the Imperial Japanese Navy.