First of all, they'll assume you are American.
Most Japanese people unfortunately think that all Westeners are Americans.
I'm German and yet they always approach me asking me in bad English: "You America?" ....
Once you tell them where you are from and if you can speak decent Japanese there shouldn't be any problems.
The people who are open-minded and interested in other cultures will be friendly.
The ones that have a lot of prejudice probably won't.
This hasn't happened to me but I heard from a lot of other people that they couldn't find real friends in Japan, because most just wanted free English lessons or a "cool accessory" in form of an exotic foreign friend, so you might want to be careful about this.