Waraenai Riyuu

From JShoujo Scans:
Kanako is the resident class outsider. She has no friends, and her classmates talk about her behind her back calling her a “downer.” However, she wasn’t always like this. Back in elementary school, she was a cheerful, outgoing girl who loved to smile. This all came to an end one day when Eiji, the younger brother of her school tutor and a classmate of hers, told her that she looked ugly when she smiled. Even though he moved away soon after, she took his insult to heart and it’s been two years since anyone’s seen her smile. Now that Eiji’s back in town, what will become of her?!