Every ten years, the Princess Jihad commences, a fierce battle to determine the Excellcia, the rightful princess among the thirteen ruling royal families. Tatemachi Ryougo, a high schooler yearning for tranquility, finds himself mistakenly contracted as a knight to Princess Orica of the Malcane house. Surprisingly, it is Princess Orica who is summoned to wield arms in battle. To enhance her strength, she must, in an unconventional manner, rely on Ryougo's assistance, starting with a rather unusual request... Will he muster the courage to aid her quest for power?