«ƸӜƷƸӜƷ» In a world where humans have lost the light from their eyes, there are beings called "hotaru" who can bring back that light to the blind people, called "kagerou", by making a contract with them. The ones who make such contract and thus regain the light are called "ageha". In exchange for giving them light, hotaru suck the life out of their contractors. Haibane is a young man who was abandoned when he was a little baby and was saved by a hotaru named Nemu, who made a contract with him. However, she could not give him the light, as she had blacked out. Hotaru are actually decresing day by day and there are those who want to hunt them down for money...