The reason there is so little racism in Japan is simple: Japanese people basically dislike everyone.
Race has nothing to do with it. We just do not want to deal with other human beings.
That is why we carefully follow manners and social rules, so we can avoid bothering one another and keep interaction to a minimum.
This is who Japanese people really are, and it is the complete opposite of Americans.
Forget hugs and handshakes. We do not even want to make eye contact. Ideally, nobody would come within 15 feet of us.
We are already crammed together on this tiny island. Everyone has had enough.
Understanding this is the single biggest key to understanding Japanese people.