Romance of the Three Kingdoms is a manuscript written by Luo Guanzhong about the events of the unification of China from 169AD-280AD mixed with historical events, myths and legends but why do Japan love it so much when the countries themselves don't really see eye to eye on culture?

The novel's influence is seen throughout Japanese history. Japan's earliest recorded events along with it's earliest stories borrow heavily from the novel as well as the war strategies, bushido code and the Samurai themselves, there was nothing quite like it.
Strong definied personalities along with the cleverest minds of the era fought a three way battle for unification, if you look at the entire Sengoku period, one of Japan's most turbulent yet most dramatized eras, it's pretty much the same setup, a battle between three major factions for the unification of Japan but with alot more players, even Nobunaga Oda is modelled and stylised on the look and beliefs of Wei General Cao Cao, so much so you almost wonder if it's the same person or history repeating itself in a different nation.
Very few nations can honestly say that they built up their heritage on their own and now reading how much one book defined centuries of codes, legends, battles and culture, you realize that Japan owes more to China than you might think as much as it pains them to admit it.