From Huffly Parfait Scans:

His name is Itou Hiroyuki, nickname Hiro-kun. He's a math teacher for the middle school section of Taihei Private School and he's the homeroom teacher of Class 3-3. He's tall, young, and really cool, yet when he's with the boys, you can't tell him apart from the students. That's the kind of person I love...

This is the author's long-awaited debut tankoubon, painfully yet gently depicting the winter days of a young girl, Haru, who fell in love with her homeroom teacher.