It occurs to me that rather than any specific person, the sword and shield refers to the ordinary citizens. Since collecting the four dragons, her travels have all been about her strength, courage, humility, passion and love for the people and how these attributes manage to win the hearts of the population at large. Ik Soo also said it will take time for the Sword and Shield to appear. It takes time for Yona’s deeds to affect the people of Kouka and for her to gain popular support. Already many of her followers will willingly lay down their lives to protect Yona and to support her. For this reason the advisor for Soo-Won now fears Yona and the power she wields.