Although Japan and China are somewhat unhappy in history, and primary school students' textbooks belittle China, the education level in Japan is much higher than that in South Korea. If you study in Japan, you will find a well-paid job when you come back.
South Korea's educational methods are more conventional, which will particularly disgust foreigners, because they will always tell these international students how powerful South Korea is when giving lectures, which will really arouse people's national sentiment, but Japan will not do so. Although Japan has a strong "national spirit", it is still remarkable in education.
There are many welfare policies for studying in Japan. If your grades are good enough, you can get a lot of scholarships, not only money, but also the tuition fees of Japanese schools are much lower than those of South Korea, so I prefer to study in Japan than South Korea.