Europe is often quoted as one example where nations were able to overcome centuries of animosity and conflict. And while there is still political bickering and resorting to silly cliches, Europe has grown together (despite marginal setbacks like the Brexit - they'll be back, lol). We understand that the boat we are all in was built on millennia of war, conflict, struggle and the ultimate realisation that together, we can progress and all win (well, theoretically).
Regardless of all the historical ballast, China, Korea, and Japan are fierce economic and political competitors. Sadly, despite all their similarities and shared values - as
@nice gaijin pointed out - they are a far cry from even considering themselves on the same page. Keeping face, inflated national pride and a false sense of racial superiority all play a role in their complicated relations. Change will not come from politicians but from future generations who will realise that their neighbours aren't so different, and wicked, after all.