Tora,Tora,Tora, ring a bell?
That was before the WW2. Not after.
Japan is a strictly hierarchical society, where the dominance/submission is firmly established in every relationship. Thus after the US beat Japan, the US became dominant, while Japan became submissive and this arrangement was never challenged.
Korea on the other hand is relatively non-hierarchical, where the people of lower standing can easily flip the decision of the superior by grouping together and has developed a culture of disobedience. Thus the king's ministers disobey the king if they don't like it, the ordinary people disobey the governors sent by the government if they don't like it, etc.
Of course this has a negative side effect as people generally disobey police too, making the Korean police officer's life hellish. Korean police officers look at the American police and complain "Look at America and Americans obey the instruction of police, while drunk Koreans throw the punch when you order them to obey the law". It's pretty amazing how the Korean society appears to be in order when there is a general tendency to disregard authority figures across the all fabrics of society.
Japanese experience this culture shock when they see the Korean drama flooding the Japanese airwave, where the billionaire's wife stand at the kitchen with the domestic side by side preparing a meal or something, and you can't easily tell who's the billionaire's wife and who is the domestic just from the screen because both are casually dressed and converse casually, and such scene is repeated over and over across hundreds of TV shows. This is not the case with Japan, where there is a strict hierarchical order established between the master and the maids, and maids all dress in maid's uniform.
It's not like a nation that been enslaved for thousands years can imagine?, guess.
The longest enslaved nation in East Asia is China, totaling 850 years since 0 AD. China only became free from foreign dominance in 1912, and the next year marks the 100th anniversary of China's regaining independence from the Manchus.