The need for us to demand the Japanese apologize over and over again in the first place
I admit that I don't know that much about China/Korea-Japan relations, but to me as a casual observer, the way Japan acts regarding WW2 seems similar to Germany in the 50s and 60s: deny, deny, deny, like a child caught in the act that cries "it wasn't me!" and expects to be believed. In case of children, it is just lack of experience with the world; in case of a nation, it is a collective delusion.
But then, it's not like China is any better with their skeletons in the closet - neither are many "Western" countries, for that matter.