Biology teacher Yuko Kinoshita, 28 years old. Serious and strong-willed, yet kind and deeply caring toward her students—an ideal teacher. Her warmth and sincerity have earned her immense trust and respect from her students, making her the central figure in class. However, one day, driven by a desire to better understand her students, she begins staying late in the classroom, cherishing the time spent with them after hours. Her presence at the lectern at night gradually reveals a new, unexpected side of her.