From the Start, I Contracted a Dragon Princess. Spare Me, Your Highness!

(Also known as: I Contracted a Dragon Princess from the Start, and Now I’m Invincible) Five hundred years ago, humanity rose up in resistance to repel an invasion by demons and monsters. By chance, people awakened a mysterious power that allowed them to form contracts with sacred spirits known as Holy Beasts. For a century, humanity used the power of these spirits to fight the demons and monsters. At last, in order to stand against them, people established a Holy Spirit Academy, where they would learn to use their spiritual energy to fight alongside their spirit companions.