Seijo Victoria no Kousatsu Auresta Shinden Monogatari

A saint unravels the mysteries of the royal palace, riddled with intrigue! Saint Victoria, who can see spirits, is doubted about her abilities and sentenced to banishment from the temple. Then, Adras, a knight from the frontier, appears before her. "I want you to use your powers to prove that I'm not the prince." This encounter changes the destinies of both of them, and they become embroiled in a conspiracy-filled struggle for the throne.

(Source: Comic Walker, translated)