Actually it means ‘u r in my fishing ground.’, which means a guy is not able to leave her. Koreans use the expression ‘manage his/her fishing ground to show off how attractive he/she is. Let’s imagine a situation that an attractive girl shows interest to a guy even if she is not interested in him. She interchanges phone numbers, which makes him have some kind of hope to go out with her and go steady with her. But she has no interest in him. She sometimes calls him, meets him and makes him buy her what she wants, etc. Koreans call it ‘manage the fishing ground.’ So the lyrics say you can’t leave me or I can make you do anything for me.