Luna, a girl said to be the “devil child” and shunned by everyone around her, encountered Jill, the princess of the Grants Kingdom, and was quickly befriended by the latter and taken under her care. Grateful of the kindness Jill has shown towards her, Luna began to train tirelessly, striving to one day become Jill’s personal knight. However, things quickly took a turn for the worst 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. Determined to save her best friend and to clear her name, Luna embarked onto the lonely journey to find the captured princess.