When the young Rekka wakes from her sleep, she finds herself in a circle of girls with beautiful ash‑colored wings behind their backs. Thus, Rekka becomes a member of the Gray‑Winged Alliance, a community that protects the city of Guri, which is surrounded by high walls. Why did she become a Gray‑Winged? Who are the Gray‑Winged? As the girl spends her days in the serene city of Guri, the secrets of her new friends begin to unravel...