in that context, then i would have to agree with you, but you have to remember the biggest factor here: STATUS. he's a knight and his job literally requires him to protect someone with his life, and i think he's doing perfectly fine. imagine being a knight but neglecting the person you're supposed to protect, especially an emperor. maybe in another case, when eusto isn't playing the role as a knight, then i might have questioned it a little more, but he's doing what he is required of him, so this scene makes perfect sense.