The story starts with our protagonist, Kakehashi Yashiro (宵宮梯子), a truant who’s already stopped going to school. On the road after running away from home, he wanders into an abandoned ruin somewhere in the city and meets an angel with only one wing. The angel grants him a mysterious power through her feathers and asks for his help recovering them, handing him a feather that bestows a special ability. The price: once the feathers are returned, he’ll forget everything.