Tonari no Seki no, Igarashi-kun.

Tsubaki Imai is the kind of quiet girl you'd never see in the center of attention. She doesn't really know how to talk to the cool kids at school like the loud boys and the bubbly girls, so she isn't exactly thrilled when she's assigned the seat next to Mamoru's, a big, unfriendly, and kind of scary guy who everyone at school seems to know. But, then, they both become class presidents, and as they start talking... This is a story about an ordinary girl who falls gradually in love... (Source: MangaPlaza)