She lives in the Roppongi section of Tokyo.
I've heard at the top of the Roppongi Hills building. Which would make it very convenient for her Music Station appearances.
All she would have to do is take the elevator down to the bottom floor and cross a walkway and boom, she's on Music Station.
I believe she also own a property on the beach, but with all the work she does in Tokyo, I would doubt she is out of her Roppongi penthouse very often.