Hyakunen Renbo

From Mousou Scans:
Eva, a long-lived witch, takes in Fernest kingdom’s youngest prince, Louis, when she is asked to heal him of his illness. Although witches are traditionally despised, Louis continues to visit her even after he is well and they form a close bond. When Louis is called back to the palace to take his place as heir to the throne, Eva must decide whether to let him go or take him back.