From Aerandria Scans:

His name is Itou Hiroyuki, nickname: Hiro-kun. He's a math teacher at the private Taihei Academy, as well as the homeroom teacher of class 3-3. He's young, cool, and tall, and yet, when he's with the male students, it's impossible to tell who are the students. He's the person I love.

This is a sad and gentle story about the 15th winter of a girl who fell in love with her homeroom teacher.

Keiko is a junior 2nd year student, but has no experience in love. One day, while going to school, she helps an unconscious 'cute boy' who fainted from anemia. Being two-faced, he doesn’t thank Keiko but instead calls her an old lady. Surprising as it is, that boy goes to her school and is a first year.

Also includes 2 oneshots: Never Let Go of Your Hand and Sweet Relationship.