Passerby

Once upon time, there was a man who was just a passerby, and there was a girl named Soteria who was about to die. They met in the land of Haveo for the first time. The man saved the girl's life, and with mysterious power, he gave her eternal life. All her life, she never knew what is the secret behind her miserable and immortal life. She never knew why the passerby did so, but "what is done can not be undone".
As for the man, no one knew his true identity and the key behind his power.
To unfold the secert, she have to meet the passerby at the end of everything when he will reveal why he kept her alive and who he really was.