Doll Isamu is one of the 3 knight dolls that protected the Doll Kingdom. He was a servant of Yae, that possessed his bracelet and amulet. But, when Yae fell in love with the grandfather of Rui, she gave the bracelet to him, for him to be protected by Isamu.
When Yae was possessed by Devaul, she sort Scarecrow to steal the bracelet from Rui, and Isamu becomes the bodyguard of Scarecrow and the servant of Yae, because she possesses his amulet, so, he must protect her.
After, Isamu refuses to follow the orders of Yae, so, he is disabled. After he to be rescued, he becomes the bodyguard of Dai when Rui rediscovers the magic words to summoning him.