The story follows Bellra Kuishuin, the eldest daughter of a Duke, who lives a privileged life filled with love from her family and attentive servants. Her world shatters when she finds herself disembodied, observing her own six-year-old body from above. To her horror, another entity awakens within her body, mimicking her life and interactions with her family. This imposter, who seems to know of Bellra's existence and refers to concepts like "otome games," acts differently from the real Bellra, performing tasks with ease that she struggled with.
Two years pass, and the imposter, now appearing as an eight-year-old, has become more refined and well-liked by Bellra's family and servants. They praise her for no longer being "willful," a trait they found troublesome in the original Bellra. The real Bellra, unable to communicate or be perceived, witnesses her family's affection shift towards the imposter, realizing they never truly noticed the switch. Heartbroken and feeling her existence fading, Bellra decides to leave her home and disappear into the forest.
As she contemplates ending her existence, a mysterious, beautiful man with white hair and yellow eyes, named Dionore, calls out to her. He reveals he can see her "fading soul" and proposes to "effectively utilize" her for his research rather than let her vanish. Dionore, a mage, explains that Bellra is a victim of a "god's prank," a rare phenomenon where souls are swapped. He offers her a new body: a homunculus he created, which lacks a soul. Bellra, desperate for connection and a chance to exist, agrees to inhabit the homunculus.
Upon entering the homunculus, Bellra awakens in an unfamiliar room, experiencing the sensation of a physical body for the first time in two years. She discovers she has white hair and yellow eyes, and her movements are clumsy, like a baby's. Dionore, who now calls himself "Papa," reveals that the homunculus is designed to be his daughter and that her existence is valuable for his research on soul transference. He assures her that she will not disappear and that he can detect any further soul-swapping attempts.
Over the next week, Bellra, now named Bellrena, struggles to adapt to her new body. She relies on Papa for movement and basic needs, while he meticulously records her progress as part of his research. Despite her initial clumsiness and inability to speak fluently, Bellrena finds joy in simple sensations like the cold floor and her own laughter, things she took for granted before. She learns that her original body's affinity for fire magic is still present in her new form, and Papa assures her that she is safe from further divine interference due to the body's acquired resistance and his own abilities. Bellrena begins to accept her new life as Papa's daughter, eager to learn and grow, while still grappling with the loss of her past identity and the lingering sadness of her family's obliviousness.
