Hime to Aiyoku no Sacrifice

Seeking vengeance, a young man named Caldo single-handedly storms the Kingdom of Solide, whose ruling dynasty has long prospered from the horrors of war.
Consumed by hatred, he forges a series of “unholy pacts” with unseen forces to ensure victory, but on seizing the castle, he seems uninterested in Solide’s people and politics, instead turning his demonic arts to the lovely Princess Fiana…