She once had the supreme honor; she was once the little princess in the eyes of every executive; but because of a fight, she turned from a noble to a commoner. He only smiled for her, but he became cold a few years later; he became indifferent because the girl in his heart left him; he was once a knight beside the two princesses; he once changed the eldest young master's character for them, but they left them. Many years later, they were invited by their school and came to their school to see if the mystery that had persisted for many years could be solved. Faced with all kinds of things waiting for them to solve, can they forgive each other?