Kou Yagami

He's the son of Kajiya, a swordsmith, and Yoshino, Queen Fuse's descendant. He was born with the jewel, which was given to Yoshino in a dream. His mother died on her way back from a pilgrimage and from helping an old professor. His father was killed by Kai's men. He seems to always regret having the jewel in his Masamune which he had no idea how to use, but always seems to know exactly what to do when it takes over, feeling that it was responsible for his parent's deaths.