AE111 Trueno brake question

Im getting a weird scrapping/clanging noise coming from my rear brakes whenever the car is in motion, anyone have any idea what it could be?? simply rusty rotors maybe?? Im in japan and the car has low miles for a 97 so it only got driven on weekends and since i bought it., i also can only drive it on weekends. the pads are new but before they were changed there was still a similar noise. Any Ideas?
Thanks in advance