A typical Japanese will not hate a person because of having a Korean ancestry. Actually there are many celebrities who have a korean background and also are very respected.(e.g. Masayoshi Son, Akiko Wada, Tomoaki Kanemoto, Akira Maeda)
Typically, Japanese people are kind and generous, and they will closely look at the person's attitudes.
The people who are not liked are the people who hate Japan and the Japanese people.
As an example, people who graduated from the Korean School (Chousengakkou) will be given an Anti-Japanese education. I heard from a Korean background person that at a Korean School, if you speak Japanese at the school, you will be beaten by your mates.
Few years ago, there were K-POP trend in Japan, and people were very interested in Korean culture and the Korean people. But when they start knowing that the majority of Korean people have huge hatred towards Japan and also the Japanese people, now many Japanese people are becoming suspicious when they hear the word Korea. It is not because they are racist or not. It is just a rule of thumb or statistics.
I admit that many Koreans have unhealthy level of hatred towards Japan as a nation, but your description neatly sidestepped the whole issue of "why", didn't it.
Koreans do remember the times when Japanese teachers would beat up Korean boys at school for using Korean, force Koreans to adopt Japanese-style names, and send young Koreans to the Pacific to be slaughtered, for the glory of Emperor Hirohito.
Personally, all the Japanese I met were nice people, and I normally don't talk history with them (I mean, what's the point?), because there are more pleasant stuff to talk about. Hopefully many others in Japan would also meet some Koreans some day and realize we are all the same people, with different historical baggages, trying to make sense in a world that doesn't make sense.
But then there are always some jerks who would say "Koreans are so mean, why do they hate Japan so much?"
Sidenote: the "Korean Schools" mentioned here are specifically North Korean (Chosen) schools. There are South Korean schools as well, but far fewer, and both are a dying breed.
Typically, Japanese people are kind and generous, and they will closely look at the person's attitudes. The people who are not liked are the people who hate Japan and the Japanese people.
As an example, people who graduated from the Korean School (Chousengakkou) will be given an Anti-Japanese education. I heard from a Korean background person that at a Korean School, if you speak Japanese at the school, you will be beaten by your mates.
Few years ago, there were K-POP trend in Japan, and people were very interested in Korean culture and the Korean people. But when they start knowing that the majority of Korean people have huge hatred towards Japan and also the Japanese people, now many Japanese people are becoming suspicious when they hear the word Korea. It is not because they are racist or not. It is just a rule of thumb or statistics.