From JShoujo Scans:

Hana is a 16-year-old girl who's a bit of a tomboy. She gets dumped by her boyfriend when she moves to Sapporo after her parent's divorce. On her first night there, she comes across a young guy who is seemingly too ill to walk. He ends up collapsing on her and is quickly rushed to the hospital. As it turns out, he's her next door neighbor, Shindou Hiroto.

The next day, when she goes to her new school for the first time, she finds out that he's actually a teacher and that he's the teacher of her class! With his out-going personality and friendly demeanor, he gets along with everyone, but she notices there's something a little different going on between him and Nishiwaki, a classmate of hers whom the others write off as a "cold-hearted beauty."

Hana always runs into him on her way to school, and as she gets to know him more, she finds herself falling for him! Things get even more messy when her boyfriend who broke up with her comes to Sapporo saying that he wants to give their relationship another shot!