Secrets of the Silent Witch, Vol. 1 (manga)

Monica Everett is the Silent Witch, the only mage in the world who can use unchanted magecraft. But underneath all the fancy titles‿she's also the shyest girl you'll ever meet. In fact, she learned unchanted magecraft just so she wouldn't have to speak in public. Monica may be talented, but she has zero confidence, and now she's being tasked with infiltrating a prestigious academy and protecting the kingdom's second prince. How will she survive.