Bill Kaulitz? or obsession?!

Bill Kaulitz was Brittany's boyfriend but due to life events they separated and broke up. Bill didn't want to break up with Brittany, meaning he became obsessed with Brittany.
Every day he called her, wrote to her, hated that Brittany was with guys that weren't him
One day Brittany went out with her friend Liang but the problem was that Bill was watching her and Bill couldn't take it anymore and went to them

Bill was Brittany's boyfriend but life events separated them and they ended and Bill became obsessed with Brittany and always watched her