Hi i am new to English language. I have seen many times when the word "in" is used to explain an area at is also used following it.

examples :

    I am living in Tokyo at Koganey
    He is staying in Sydney at Camden
I want to know that why it can not be written as 

    I am living in Tokyo in Koganey
is there a rule to follow when writing like this ?

i will be grateful if you could give a clear explanation about this.