A heroic knight from another realm, Arnelia led a rebellion against the cruel Demon Queen Valvaran, uniting warriors and forging an army for the final battle. During this confrontation, Valvaran enacted a reincarnation ritual that transported Arnelia and her comrades to modern-day Kyoto. While her fellow heroes reincarnated in human bodies, Arnelia manifested as a dog, taking residence above a candy store inherited by art student Kumi Honamanuma. This store became their base in the new world.

As their former leader, Arnelia retained her serious and dutiful nature, relentlessly prioritizing the mission to gather scattered fragments of Valvaran's power. These fragments caused ordinary objects to transform into monsters, threatening Kyoto's peace. Though the demon queen reincarnated as a seemingly non-hostile elementary school girl named Ran, Arnelia harbored deep distrust, constantly questioning Ran's intentions and sincerity. This skepticism frequently placed her at odds with Kumi, who advocated for trusting Ran.

Arnelia continued managing her team of reincarnated heroes. She expressed frustration towards members neglecting their duties, particularly Mai Hasaka's pursuit of an idol career. Her protective instincts remained strong, especially concerning Harami Sanno, a former berserker whose absolute loyalty to Arnelia endured. During a battle against a Flame Giant monster, Harami followed Arnelia's commands without hesitation despite sustaining injuries. Arnelia's strategic mind persisted, though her canine form restricted direct combat, leading to moments of dry humor as others reacted to her appearance.

Character development saw Arnelia gradually accept the new world's peace and Ran's genuine change. She shifted from confrontation to cooperation, acknowledging that the collected demon fragments could resolve conflicts without violence. This evolution reflected her core traits of responsibility and adaptability as she balanced knightly duties with the absurdities of everyday Kyoto life.