Prologue: Meeting a Devil

Y/N wakes up one day in an alley and doesn't remember anything except his name. He soon comes across strange beings and discover they have decent battle skills. He attracts the attention of a powerful Devil with an appearance and personality that is different from her actual age. She offers to help him regain his memories and help him get a grasp of his abilities. Soon Y/N will discover his true nature and uncover the secrets of a sentient darkness trying to consume the world. Will his past define who he is?