This is the story of Luna, a girl said to be the "devil child" and was shunned by everyone around her, living a secluded life. Fate finally smiled upon her as she encountered Jill, the princess of the Grants Kingdom and a young girl of Luna's age. Unwavered of the stigma placed upon Luna by the masses, Jill quickly befriended her and took Luna under her care. Grateful of the kindness Jill has shown towards her, Luna began to train under Rahab, the knight captain who has adopted her, striving to one day become Jill's knight.
However, things quickly took a turn for the worse as Luna accompanied the princess onto an expedition for her coming-of-age ceremony. A group of bandits ambushed them at the destination, killing most of their escort and kidnapping Jill, leaving Luna as the sole survivor of the encounter, who returns to Grants with a parasite planted inside her by the bandit leader.
Upon her return, Luna was swiftly condemned and thrown into prison for losing the princess. With the help of her former comrades, she escaped from prison and was then branded as a traitor. Determined to save her best friend and to clear her name, Luna embarked on the lonely journey to find the captured princess.