Secrets of the Silent Witch, Vol. 2 (manga) — Matsuri Isora

Monica Everett, the powerful but incredibly shy mage, just wants to carry out her mission to guard the second prince in secret. Yet her dreams are shattered when the prince takes notice of her talent with numbers…and appoints her to be the student council's accountant! Now she must not only deal with envious students but also receive instruction from the icy Cyril. However, behind her instructor's cold exterior lies a secret -- one that only the Silent Witch can resolve…