Half-Japanese American who lived in Japan half his life.  Have you heard of the Yayoi people?  So we know the Yayoi entered Japan via the Korean peninsula, if there wasn't a land bridge a long time ago.  What does that mean?  In essence that the Japanese and Koreans are akin to cousins.  The Japanese, despite the propaganda, were NEVER homogeneous and I'm sure the average Korean and Chinese knows this.  

I discovered a long time ago, having read an article about burial mounds in Japan's first capital, Nara, and how that was for the Imperial family members.  Well, Emperor Akihito, in 1991 admitted it.   "I, on my part, feel a certain kinship with Korea, given the fact that it is recorded in the Chronicles of Japan that the mother of Emperor Kammu [Niigasa] was one of the descendant of King Muryong of Baekje."

Ugly history I know, but hopefully Japan and Korea, Japanese and Koreans can become the best of allies.  Younger people in both countries don't seem to harbor ill will towards each other, which is good, and really if anyone should it's Koreans.  Last thing about this, in a Facebook group of "haafu", i.e. half-Japanese peeps from various countries, I set up a poll asking people if they got traces of Korean or not.  42% said YES, 57% said NO, 1% didn't want to disclose.  I got 1.4%.

Peace and best wishes to you all!