The math teacher at Taihei Academy, Itou Hiroyuki, also known as Hiro-kun, is the homeroom teacher of class 3-3. Despite being young, cool, and tall, his appearance is so similar to his male students that it's difficult to distinguish between them. He's the person the protagonist is deeply in love with. This story depicts the sad and tender emotions of a girl experiencing her 15th winter while harboring feelings for her homeroom teacher.