Spiral S5 - Ayumu Narumi's older brother Kiyotaka Narumi, a renowned detective and piano player, suddenly disappears. His last words - "I'm Going to Pursue the Mystery of the Blade Children". Two years later a row of murders and incidents begin, all relating to the Blade Children. Together with school journalist, Hiyono Yuizaki, Narumi tries to figure out their destiny and the truth about what happened to Kiyotaka.