In spring 1592, Japanese ships landed in Busan, Korea, intending to invade the country and find passage to China. This was the beginning of the Imjin War, or Seven Years War, between Korea and Japan, and the beginning of a difficult relationship between the two East Asian countries. In the late 1800s, Japan was an emerging country that wanted to protect itself, and Korea was seen as a threat. Nothing personal; just a little too close for comfort. Japan sought to annex the country before someone else---someone more dangerous---could. To get Korea, Japan fought China for several months between 1894 and 1895 and fought Russia between 1904 and 1905, winning both. So, on 22 August 1910, Japan officially annexed Korea.
For thirty-five years, Koreans endured harsh colonial rule. This period in Korea can be considered a "cultural genocide" because of the suppression of the Korean language, removal of Korean artifacts, modification of old songs and poems to refer to Japanese emperors instead of Korean emperors, and physical alteration or destruction of Korean temples and monuments. On top of that, the Korean people suffered immeasurable pain and destruction. Some people were burned or buried alive, some men were conscripted into the Japanese military, some women were forced to serve as "comfort women" to Japanese soldiers, and some families were forced to change their surname to a Japanese name.
While some scholars argue that Korea gained some economic benefits during the Japanese Imperial Period and suggest that things could have been worse if Russia or China had won the opportunity to annex Korea instead of Japan, this period definitely didn't improve the personal relationship between the Koreans and Japanese.
Today, the Japan-Korea rivalry surfaces in the dispute over the ownership of Liancourt Rocks, two small islands known as Dokdo ("solitary island") in Korea and Takeshima ("bamboo island") in Japan. The islands, currently occupied by Korea, are located roughly halfway between South Korea and Japan in the East Sea. Small and rocky, there's not much to see on the islands, but they're located in a valuable fishing area and could potentially hold natural gas reserves. Both countries are desperately searching old documents and maps for proof of territorial claims.
In July of this year, the Japanese government decided to mention the dispute in new junior high school textbooks and claim the islands as Japanese. Around the same time, the US Board of Geographic Names changed its listing of Liancourt Rocks from South Korea to "Undesignated Sovereignty." Korean politicians and citizens protested both issues, and the US quickly reversed its decision and relisted the islands as under South Korean control. At the height of the "textbook scandal," the South Korean government temporarily removed its ambassador from Japan and protesters killed live pheasants (the Japanese national bird) in demonstrations in Seoul.
When asked to make a poster advertising Korea, one group of my students chose to make a poster advertising Dokdo. Looks like the Japan-Korea rivalry isn't going away any time soon.