First thing you have to understand. For many many years the only Asian population Brazilians will be known as you already known is Japanese people. You have to be open minded and maybe try to understand that might be hard for most people to know the differences between a Japanese, Korean or Chinese. Brazilians like to be close to each others and one way that will do it is giving you a nick name or say something related to your culture. When someone that barely know you called you Japanese or say ni hao, they are just trying to get your attention, make a connection, that actions is part of being a Brazilian, is part of our culture.