Excellcia to Shoukan Kishi

Excellcia to Shoukan Kishi (冠絶の姫王〈エクセルシア〉と召喚騎士) is a light novel series by Amane Miyazawa with illustrations by Pyon-kti.

Plot
Once a decade, a battle called the Princess Jihad is held to determine the Excellcia, the true princess from among the thirteen royal families who control the world. Tatemachi Ryougo, a highschooler who desires peaceful days, is mistaken by the Malcane house's princess, Orica, and is binded into a knight contract. "Come! My Summon Knight! No, why am I the one armed!?" Somehow, it was the princess Orica who is summoned as a knight to fight. And in order for her to become strong... "Will you e-eat it for my first?" She must arouse Ryougo!?