My Annoying Little Big Sister Is The Pontifex Maximus!?

Ancient Rome AU. Altare Regis, the newly minted Praetor of Rome is tasked to lead Legio V - Stella Elysium to do battle with the Doubter tribes. But before all that, he must visit the newly appointed Pontifex Maximus, which to his dismay, just so happens to be his small, big sister Kobo Kanaeru. Things quickly get out of hand!