Kimi ga Hikari

Shinohara Sumi is stuck taking supplementary lessons in the heat of summer. Her situation immediately changes when a mysterious boy named Yoshino Mitsuru jumps into the classroom through the second story window. He spends each day helping her with her lessons, and her feelings for him begin to grow. But things may not be all that they seem as she begins seeking the reasons for the loneliness in his eyes… (Source: MU)