[GoNative]

I guess the point Rick is making is that regarless of how hard you try, regardless even if you become a Japanese citizen, you will never actually be considered Japanese by the Japanese. In places like Australia and I assume the US it's not unusual at all to see people of many different racial backgrounds and to consider them Australian or American without a second thought.
In Japan it's not like that. You could be born there, speak and read absolutely fluently, know the customs as well as any native but unless you look Japanese you will never be considered Japanese. You will always be a gaijin.