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is it a rule to put at after in?

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.

thanks