Hishintan - vita arcana manga

Hishintan - Vita Arcana summary:

It's 217 AD, several decades after the end of the "Pax Romana," and the Roman Empire is still the most powerful empire in the world. However, between corruption in the government, increasing attacks from savage hordes, and continuing resource-draining foreign campaigns, the power of Rome is on the decline. With the recent assassination of the emperor Caracalla, many things are about to change...