Faded Away Volume 1 - Qiseki

Sou and Mitsuko met as children, but one day Mitsuko suddenly disappeared. Sou waited. Waited for so long he started to believe that his friendship with Mitsuko was all in his imagination.  Years later, Sou is in high school when a mysterious new student arrives. Mitsuko has re-entered his life and while she hasn't changed, Sou has.