First, the 12th century is out of my field, which begins in 1567 and ends in 1807. Nonetheless I'll try my best to answer this question. I may be incoherent at times, so please bear with me.
1115 in Korea would have been during the Goryeo Dynasty, which we know much less about compared to its successor. One reason is that its bureaucracy was much less concerned about record keeping, illustrated by the fact that the length of the Annals^1 of the Goryeo Dynasty was less than a tenth of the length of the Annals of the Joseon Dynasty. Worse, the Annals of Goryeo and many other texts from the period are no longer extant. Historians instead often rely on even shorter histories such as the Goryeosa. This means that all in all, we have a rather incomplete view of this dynasty.
But for the most part, Goryeo and Koreans of the time had a cordial relationship with the Japanese. We know maritime trade was common between the two in the 12th century. For instance, here's a typical Goryeosa entry from 1148:
日本都綱黃仲文等二十一人來
Twenty-one people came [as traders] lead by the Japanese merchant Hwang Jungmun^2
Furthermore, there appear to have been very few/no Japanese pirates around Korea in the entire 12th century; the last Japanese pirates mentioned in the records were in 1093, and even that was not strictly Japanese but included a dozen Chinese pirates as well.
Hence the Japanese would probably be thought of generally positively as a mostly peaceful neighbor and trade partner. A Song Chinese trader might be held in higher regard given the age-old Chinese connection to civilization, but the modern Korean image of the Japanese invader would have been rare to nonexistent in 1115.
^1 "Annals" or "True Records" were daily court records of East Asian polities. They originate from China (example) and besides Korea the system also spread to Vietnam and Japan.
^2 This is what the Koreans called him, not his Japanese name which we do not know.