Waraenai Riyuu

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 didn't always use to be 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 "fugly" 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 though, what will become of her?!
(Source: JShoujo).