Prism (Higashiyama Shou)

Riding high on the memory of a boy named Hikaru with whom she spent a day during her last year of grade school, Megu went through middle school without romance. Now that she's a high school student, she has decided she is finally completely over her first love and can look towards the future. Shikashi! Megu meets a pretty girl on her first day of high school who gives her a big hug, and her name is Hikaru?!