Story: 

    Spiral is a mystery story the focal point of which is the nature of the Blade Children, those who have cat-like eyes and are missing a seventh rib bone.
Ayumu Narumi's older brother Kiyotaka, a famous detective and pianist, disappears without a trace. The only clue as to his whereabouts is the "Blade Children", the only words Ayumu managed to catch in a final phone call from Kiyotaka. Two years later, a row of murders and incidents begin, all related to the Blade Children. Together with the infamous (and only) school journalist, Hiyono Yuizaki, Ayumu tries to figure out their destiny and the mystery shrouding their past.