Sain is a secondary character in Fire Emblem, and makes minor appearences in the Spotpass and DLC content in Fire Emblem: Awakening. He is half of Fire Emblems represenatives for the Red/Green knight team, acting as the green to Kent's red.
Sain is a flirtacious and light hearted knight of Caelin, sent by the Marquess to find his estranged daughter and her family. He and his partner, Kent, only find the Marquess's granddaughter, Lyn. The two become close to the girl, and stay as her friends and knights after she reclaims Caelin from her uncle. Sain finally finds love after or during the events of Fire Emblem, and remains as a skilled knight in Caelin after Lyn leaves.