Reyson is a character from the games called Fire Emblem... Same as Soren. He's the heir to the Heron kingdom. He has lost all of his family but his older brother and younger(?) sister. He lived with the Raven Clan... or was it the Hawk Clan... Anywho, This character isn't for this story.
In Elyasia, Reyson is the last few of the Heron demon clan that lived in the southern lands. He lost his family and was once thought dead yet he was one of the few that lived. Much of his past is unknown.
Reyson himself is a friend of the southern princesses and Lady Kira once thought of having him as Mira's knight but it didn't happen since the princess was too young for a knight and he didn't like the idea.
Yet as time past, he kept his friendship with Lady Kira and even with Mira who came to call him, her bird.
His nickname is Lost Bird to Mira since to her, he's like a bird who lived his whole life in a cage.