Since childhood, Karen dreamed of becoming a teacher. She tried her best and finally realized her dream. After a week of internship at the new school, she was assigned to be the homeroom teacher of a class. She tries to memorize students' names, calling them by nicknames. Karen is very popular with the students and they all love her except Hayato. He often skipped school and fought with students from other schools. Karen wants to help him and wants him to open up to her. She often meets and talks with Hayato, writing in the same diary as him. Gradually, feelings formed between the two. Even though she knows this is not allowed and will probably ruin Karen's childhood dream, she loves Hayato! Run away together to go on dates, go to hot springs together, enjoy the moments of being a couple. I love you. After you graduate, let's get married. A beautiful but forbidden love, two people are separated but their hearts will be together forever.