What Bad Intentions Can a Substitute Have?

In a big adventure, she hooked up with the school bully, she wanted money and he wanted sex. "One hundred thousand a month to be my girlfriend." "Must be on call." "Remember your identity and don't interfere with what I do." Later, his Bai Yueguang returned to China and provoked her, saying that she was just a substitute. She: It's so funny, I don't know who the substitute is.