Prism

School girl Megumi, suffering from an uneventful life after a fleeting grade school romance, hopes to end such boring days with her entrance into high school. Still dreaming about the peaceful days with her past love, Hikaru, she encounters a stunningly beautiful girl on her way to the entrance ceremony. Suddenly, the girl calls out for Megumi and gives her a hug! Hikaru enters back into Megumi's life not only as a classmate, but as a girl. How will Megumi handle the shocking revelation?

(Source: Dynasty Scans)

Note: this manga is currently on hiatus due to its author's copyright infringement. There has been no notice since June 2012 about its re-appearance.