I think what he's saying is that he believes he needs to protect this other person. What surrounds a kingdom? A wall; protection; safety. He seems to take it a little far though, going so far as to know when she comes home and to be able to recognize her car easily. Maybe a song about obsession? Or a police officer, keeping watch over someone in danger (or a suspect?)? These are all things that occur to me.
I think what he's saying is that he believes he needs to protect this other person. What surrounds a kingdom? A wall; protection; safety. He seems to take it a little far though, going so far as to know when she comes home and to be able to recognize her car easily. Maybe a song about obsession? Or a police officer, keeping watch over someone in danger (or a suspect?)? These are all things that occur to me.