Help me recall thing manga please... astronomy & "Sora" something?

Highschool setting: Lead character(Guy) comes back to hometown, a weird childhood friend(girl) obsessed with astrology, which he hates by the way because he calims to have been harassed into outdoor activities [he's quiet & just like reading books] finally breaking his arm or something like that... anyway, she forces him to join "Astrology" club.... I remember a scene she released paper stars off their school roof like a stunt to get new recruits... been out of touch with manga over a year..

any help? - ithink there's a "Sora" or something in the title... thanks to whoever answers!