When Yothaka's mother marries Chatcharun's rich father, Chatcharun is not happy. He believes that her and her mother are both gold diggers. Also, Yothaka has just returned from abroad and has a care-free "western" attitude. She is a rebel at heart, while Chatcharun is conservative. Along with believing she is a gold-digger, he also thinks she is "easy". She encourages that misconception just to annoy him. He harasses, she teases. They bicker. A lot.
