Kimi wa Yotsuba no Clover

The romantic suspense manga centers around Uichi, a once popular student who is now relentlessly bullied in high school. Still, he strives everyday to keep a promise to Yotsuha (his first love from elementary school before she transferred schools) to become a veterinarian. Just as he reaches his limit with the bullying, Yotsuha suddenly appears before him. She has seemingly not changed since back then — except she harbors only one hidden resolve deep in her eyes.

(Source: ANN)