1998 Nissan Skyline Back Breaklight wont turn off, even wit

Brakes problem
1998 Nissan Skyline 6 cyl Automatic

Hello.
I have a 1998 Nissan Skyline. Recently, the back break lights will not turn off even when the car is off. Aka the engine not running or keys in the starter. It always does this and I have to unplug the car battery when I am not using the car so that the lights being on wont run it out. There are no lights lit up inside the car and there do not appear to be any other problems. I just don't know where to start. Please help! I;m trying to sell my car in the next few weeks. I live on Grand Cayman and repairs here are very expensive so I'm trying to do it all myself.