Reborn to Master the Blade: From Hero-King to Extraordinary Squire ♀ (Manga) Volume 4 by Hayaken

Reincarnated as a girl far in the future, former Hero-King Inglis has the chance to hone her fighting skills. Now fifteen years old, she sets off for the royal capital to enroll in the knights' academy with her childhood friend, Rafinha.
While stopping in a town along their journey, they befriend the Highlander, Cyrene; despite her position, she loves the people of the surface, and her citizens return her love in kind. But then one night, a Magicite Beast awakens and wreaks havoc upon the town—and its identity is none other than the paragon of peace, Cyrene!