From NOIR:
Memory eaters live on people's memories. They are originally death messengers who remove a human's memories when they carry souls. But some of them are charmed by the beauty of the memories and become Exiles: Memory Eaters. Dio is one of them, but instead of stealing human memories like other Exiles, he earns them by helping people. One day, Dio finds a girl who is losing too many memories from Exiles. He tries to help her, but Ces, who was a model death messenger, is around her. What is he doing here?