+c sword and cornett manga

+C: Sword and Cornett summary:

There was once a hero who vanquished the darkness of the land and liberated the people. He then built a kingdom, and had his descendants rule as kings. Although they had ruled the land for so many years, in reality, political power was being wielded solely by the aristocrats of each region. One day, this seemingly peaceful kingdom was disturbed by the mysterious death of the principal heir to the throne. The sequence of events that this assassination set into motion, would soon come to involve all of those with the right to become the next king...

There's the spin- off: