It seems easier to fall in love with a stranger than a person you know well. This is probably because love for a person you are close to wears off over time. I think the relation between Korea and Japan is little different from this kind of relationship. It was Japan's annexation of Korea that caused two countries' good relationship to turn sour and their mistrust in each other to deepen. Then, what's needed for Korea to re-embrace Japan as the saint said, even though the nation inflicted a painful memory and deep wound in the modern Korean history? The process should start from academic reconsideration of Japan's annexation of Korea and conclude with Japan's apology and remorse for it.
As widely known, in an attempt to annex its neighbor Korea, Japan had to formulate both the thorough self-denial logic that it's not an Asian nation and the circumstantial logic that imperial powers including the United States enthusiastically backed its annexation of Korea. And in the Japan-Korea Annexation Treaty, Japan tried to justify its forcible occupation of Korea by proclaiming that the treaty was concluded "to achieve the goal of securing permanent peace in the East."
Did the world support Japan's annexation of Korea?
Then, how can Japan explain the fact that Korea regained independence and peace was restored in the East following the end of the Pacific War that broke out by Japan's sudden attack on the US. Is it true that the US accepted Japan that pursued "Ex-Asian" westernization as a member of the Western powers and supported its occupation of Korea? Doesn't the hypothesis that the US approved Japan's occupation of Korea (even in Korea, Akifumi NAGATA's book The US Dumped Korea is translated and published) reflect Japan's intention of holding others accountable for the annexation?
In the imperialist era, Japan might be able to coerce a neighboring country in Northeast Asia, but on the global stage, it was seen just as an emerging nation in East Asia. Imperial powers continuously kept Japan's expansion at bay with strategies like the Triple Intervention (1895), which was implemented shortly after the end of the Sino-Japanese War to contain Japan's invasion of the continent, and the attempt of 2nd Triple Intervention (1908) between Germany, US and China made in the wake of the Russo-Japanese War. Since the Taft administration of the US formulated its East Asian policy in March 1909 based on "open door" and "preservation of Chinese territory" in particular, the policy ran directly against Japan's continent invasion policy which regarded Korea and South Manchuria as trophies.
In the end, Japan stood at a crossroads of decision: whether to give up its plan to monopoly Korea and South Manchuria on the advice of Western powers? or to annex Korea and dominate South Manchuria by taking the risk of confronting the US? Unfortunately, Japan chose the latter path, which led the nation to go to war with the US, rather than create a counterbalance.
In this light, Korea's pioneer Danjae Shin Chae-ho's editorial entitled "Manchuria and Japan" published in The Daehan Maeil Shinbo (January 12, 1910) gives many implications to us with regard to the nature of Japan's annexation of Korea:
"There is a widespread rumor that an agreement was signed between China and Japan. Will the Western powers that are fiercely and ferociously looking all over Asia let the two nations - Russia and Japan - run freely across Manchuria which is the most crucial land on the mainland China and has all the important interests of the time and just watch Japan - the small island country in the corner of the East - strut? … Dear Japanese, the earth belongs to the people of the world and the world won't let Japan do as it pleases. So, isn't it wise for you to take a road to true peace of the East, strengthen your position and sustain happiness of the East?"