Romantic hate is defined when you hate someone, but you have a connection with them. You are the person's enemy, but you are always with them and you can't look away from them.
Those two hate each other , but they can't look away from each other. They must romantically hate each other.
Sam: I hate him, but I can't get away from him
Bob: You must romantically hate him.
Sam:Really?
Bob: Yep. Romantic hate is when you hate someone, but you can't get away from them.