He and she were childhood sweethearts. In front of outsiders, they were brothers and sisters, but they did have some unknown secrets. He, his classmate, knew that he had fallen in love with this innocent and ignorant girl the first time he saw her. She, the girl that the family favored, was engaged to him. When he met her without any objection, he found that it was not bad to fall in love with someone, but the facts were confusing. He, a classmate whom she had not cared about since childhood, had a secret crush on her for ten years. She, happy to be enemies, eventually became good best friends.