In a future where human-like robots called hIEs are commonplace, a compassionate high schooler named Arato Endou finds himself thrust into a dangerous situation. He's saved from a rogue hIE attack by Lacia, an advanced and enigmatic hIE who offers him a deal he can't refuse.
To ensure his survival, Arato must become Lacia's owner, taking responsibility for everything she does. Despite her warning that she lacks a soul, Arato agrees, and Lacia moves into his home.
Their lives become intertwined as Lacia adapts to her new, peaceful surroundings. However, the circumstances surrounding Lacia's existence and her escape from a powerful corporation hint at a larger conflict brewing, promising a journey full of intrigue and potential danger for Arato.