If Nazis believes Aryans were the superior race, why did they ally with the Japanese?

According to Ian Kershaw in "Hitler" it was because Hitler respected the Japanese because he saw them as the Asian version of Germans. He thought that they had great pride in their race as they didn't mix with others. In Hitler's mind the different races shouldn't mix as it would produce inferior offspring which would weaken the nation. The nation of course being above the individual in his mind.