The story begins with the protagonist, referred to as "I," experiencing fragmented memories of a happy childhood filled with family and school life, which abruptly transition to a stark white void and then darkness. Awakening in a desolate, grey world with a distorted landscape and a featureless sky, "I" discovers a horrifying truth: "I" no longer possess a physical body, existing instead as a shifting, gas-like entity. Despite this shocking revelation, "I" quickly adapts, accepting this new reality. Unable to recall a name or any personal history beyond fragmented memories of a school uniform, "I" deduces "I" was likely a student, possibly a middle or high school girl.
Boredom becomes a primary concern in this empty world. "I" discovers a peculiar habit: small, insect-like creatures appear, which "I" can "pat" to make them disappear, leaving behind a sweet, honey-like scent that provides a sense of satisfaction. This becomes "I"'s daily pastime. Over time, "I"'s amorphous, brown form solidifies and darkens, eventually resembling a slime-like substance.
A turning point occurs with the appearance of a magnificent, horse-sized black panther. Initially terrified, "I" is captivated by its beauty. To "I"'s surprise, the panther communicates telepathically, questioning "I"'s lack of fear. "I" learns that this world is the "Spirit World," a realm inhabited by beings without physical bodies. The panther, a powerful demon known as "Dark Beast," explains that spirits and demons are of equal standing, but demons lack the intellect of spirits. He also reveals that beings in this world are called "Demons" by humans.
The panther, intrigued by "I"'s ability to understand him and "I"'s unique form, decides to teach "I" how to solidify "I"'s body. "I" initially desires a human form but is advised against it, as starting with a human form is considered foolish and weak. Instead, "I" chooses a cat-like form, inspired by the panther. However, the solidification process results in "I" becoming a small, golden kitten with bat wings, a form that greatly amuses and frustrates the Dark Beast. He decides to keep "I" as his "pet," a decision "I" accepts, finding comfort in the companionship.
Life with the Dark Beast continues, with "I" growing into a more agile kitten. "I" learns about the Spirit World's division into the "Spirit World" and the "Fairy Realm," and that humans refer to their inhabitants as "Demons." "I" also discovers that the Dark Beast, despite his power, is an anomaly, as most demons are unintelligent and violent. He explains that demons are called "Demons" by humans and that his own species is called "Dark Beast," while "I" is designated "Golden Beast."
A significant event occurs when "I" accidentally activates a summoning circle, drawn by "I"'s human memories and a desire to return to the "light world." This leads to "I" being forcibly summoned to the Material World. The summoning is incomplete, and "I" is reborn as a human baby named Yulcia, possessing the memories of both a demon and a human.
Yulcia's new life is one of privilege and overprotection. Her mother, Ria, and the household staff are doting, especially after Yulcia miraculously survived a stillbirth. Yulcia, retaining her demon knowledge, struggles with the limitations of her human infant body and the unfamiliar world. She discovers that magic exists and that she possesses strong aptitudes for Summoning and Holy Magic, despite her demon nature. Her unusual abilities and appearance cause fear and awe, leading to her being treated as an "angel" or a "precious child."
Her father, Fort, is distant but loving, and Yulcia's attempts to connect with him are met with his own insecurities and a fear of her otherworldly beauty. Yulcia's unique nature and her interactions with others, including a young noble named Sherry and a boy named Rick, hint at future complexities. The story culminates with Yulcia, now a toddler, being drawn into a dangerous situation involving a kidnapping attempt at a noble's party, where her unusual presence and abilities begin to attract significant attention.
