Japan and South Korea are both supposedly democracies in the "western mould", but both still maintain a gloss of authoritarianism. North Korea...well, that's another thing entirely...
Bit of a sweeping statement, don't you think? Given Korea's geo-strategic importance throughout the second half of the 19th and all of the 20th century, they haven't really had much choice but to be "promiscuous" in terms of alliances.