Sensei Ni, Ageru

Azami is a particularly boring 14-year-old. She has no friends, she spends all her time studying, she’s never fallen in love…until one day, her sister lends her a fancy dress, and she meets the boy she’s never dreamed of.
Azami meets Makoto when he stops a thief from stealing her purse. Over the next few days, they end up bumping into each other quite frequently, and Azami starts to feel love for the first time. It seems like Makoto’s falling as well. He tells Azami that she reminds him of someone he knew…
Azami, in a uncharacteristic act of boldness, decides to kiss Makoto. They part, and the next time they see each other is at Azami’s school– he’s her new teacher.
(Source: Ai's Bookshelf)
Included one-shots:
Volume 2: Innocent World: Hitoribocchi
Volume 3: Innocent World: Setsunai Kimochi