How did Ki-ja the Hakuryuu (the White Dragon) get this scar? In the preview for Episode 10 of Akatsuki no Yona, it was shown that Ki-ja had this scar on his back.
It is revealed in Chapter 70.5 - Extra Chapter: Upon That Back of the manga and in the OVA Akatsuki no Yona - Sono Se niwa.


   It was caused by the previous White dragon, who was also Ki-ja's father, at the moment of his birth as a mark of desperation.