As you know, k-pop is very popular these days in Japan. For example, TOHOSHINKI and KARA are very famous k-pop groups in Japan. In the beginning, such a popularity of Korean culture started in TV dramas, for example, Fuyu no sonata among elder Japanese women. As time goes by, Korean culture becomes popular in k-pop and TV dramas, for example, Ikemenn dusune among young Japanese girls. Moreover some young Japanese girls began to have interested in Korean fashion, Korean food and traveling to Korea. Some young Japanese girls want to have a Korean friend from interest in Korean culture.
What does this tendency influence to Japanese? I think that good feeling to Korea and Korean people has certainly increased among most of Japanese. These days, Korea is an exciting country for most of young Japanese, and it contributes to this liking that the closeness and cheapness between Korea and Japan when Japanese travel to Korea. The flight to Korea is within about 3 hours, we can go there to pay only from 30,000 yen.
However, of course, not all Japanese become to have good feeling to Korea due to this popularity of Korean culture. Older Japanese tend to be difficult to have good feeling to Korea. In addition, there are some Japanese who don’t have good feeling to Korea as the popularity of Korea spreads, because as it spreads, existence of Korean culture becomes emphasized. So this popularity of Korean culture is making two opposite feelings among Japanese, but it is true that the popularity of Korean culture has produced feelings of familiarity with Korea.
Why can the popularity of Korean culture in Japan make not good feeling toward Korea? The reason is that we have a negative history between Korea and Japan. In 1910, Japan colonized Korea, and now there are a lot of Koreans with permanent residence in Japan, who have some difficulties, for example, discrimination, problems about their identity. Moreover some Koreans feel bad to Japanese and some Japanese feel bad toward such Korean’s reaction.
Due to this popularity of Korean culture, Korea is certainly becoming a familiar county among young Japanese. It is pleasant that the friendship between Korea and Japan will increase much more in the future. However, we must know history of two countries and various opinions of various people of these countries before enjoying the products made by culture of other country.
by ayako miyamae
JAPANsociology 
source: Nothing
I agree. Japan and Korea still have lots of issues like responsibility of the war or the problem of comfort women. I hope the K-pop will help us understand each other, particularly for younger generations.
I almost agree your opinion. However, your answer about the reason why the popularity of Korean culture in Japan can encourage Japanese people to have bad feeling toward Korea is too vague, I think. Some Japanese people have their various doubts about Koren boom in Japan. That too much information about Korea and biased report by Japanese media supported by Korea are often criticized is typical of them. Of course, we cannot say that what they say is correct, but these point cause controversy.
The negative history between Korea and Japan is related to this problem and can be core factor, but as for this problem other some reasons can be also considered.