Too-Perfect Saint: Tossed Aside by My Fiancé and Sold to Another Kingdom (Manga) Vol. 6

Mia is determined to bring down all who betrayed her sister, starting with exposing Second Prince Julius at a royal banquet. After the fallout, the country turns its attention to preparing for the demonic invasion. Mia does her best to contribute, but her powers as a Saint have nearly reached their limit. Meanwhile, her sister Philia races back to her homeland after a failed attempt at expanding the Great Purification Circle. As the demonic threat rises, can Philia make it in time to save her younger sister?