Since she was little, Karen dreamed of becoming a teacher. She worked hard and finally realized her dream. After a week of interning at a new school, she was assigned to be the homeroom teacher of a class. She tried her best to memorize her students' names and called them by nicknames. Karen was very loved by her students, and they all cherished her, except for Hayato. He often skipped school and fought with students from other schools. Karen wanted to help him and hoped he would open up to her. She often met and chatted with Hayato, writing a diary together with him. Gradually, feelings developed between the two. Although she knew this was forbidden and could jeopardize her childhood dream, Karen loved Hayato! They ran away together to date, went to hot springs, enjoying moments as a couple... "I love you," "After I graduate, shall we get married?"... A beautiful love but forbidden, they are separated, but their hearts will always be together...