Ferdinand is the head priest in the temple of Ehrenfest, as well as the patron and educator of Myne in the temple. Ferdinand teaches and guides her to be a 'proper' shrine maiden and noble lady.

Ferdinand is a serious, disciplined and pragmatic person. He has a bit of a fussy personality, leading him to take on all sorts of responsibilities, including Myne's education. Ferdinand is meritocratic in spite of his social status, despising incompetence and laziness the most, and earning him the reputation of a harsh disciplinarian who would cut off anyone who couldn't meet his standard. The same trait leads him to favor Myne ever since their first interaction, calling her worthwhile to educate.

(Source: Ascendance of a Bookworm Wiki)