The story begins with the protagonist, who recounts her past life as a frail child with a weak heart and immune system, confined to a sterile room. Facing death, she desperately wishes for a strong, invincible body in her next life. Her wish is granted, and she is reborn as Mary Regalia, the daughter of Duke Ferddid and Duchess Aries Regalia in the fantasy kingdom of Aldia.
As Mary grows, she retains her memories from her previous life. At one year old, she is already crawling and observing her luxurious surroundings, realizing she is a noble. By age three, she can walk and converse, though she deliberately acts like a normal child to avoid suspicion, despite her advanced mental age. She discovers that Aldia is a world of swords, magic, monsters, and spirits, akin to an RPG. Her primary goal is to live a long, peaceful life and repay her parents, avoiding unnecessary risks. She also finds herself understanding the world's language and script effortlessly, attributing it to divine intervention.
A turning point occurs when, at an unspecified age, Mary accidentally stops a heavy wooden box from falling with a single hand, revealing her extraordinary strength. This incident stems from a visit from her father, Duke Ferddid, a former marshal, who introduces her to her future personal maid, Tute. Mary, initially excited to have a companion her age, befriends Tute. However, during a game of hide-and-seek in a barn, Mary's strength causes a pile of wooden boxes to collapse. Instinctively, she stops the falling boxes with one hand, an act that terrifies Tute and leaves Mary deeply shaken by the fear of rejection. This event leads to Mary's withdrawal and fear of her own power.
Later, at age six, Mary's strength continues to manifest, causing her to accidentally break objects. She confides in Tute about her past life and her unusual strength. Her father, protective and dismissive of her need for martial arts, only exacerbates her overprotective upbringing. At age seven, Mary learns about the "Oracle Ceremony," a ritual where seven-year-olds receive divine guidance about their potential. She hopes this might provide an opportunity to learn martial arts.
During the Oracle Ceremony, Mary's immense power is revealed. The ceremony involves touching a crystal that measures one's potential in combat, intellect, and magic. Mary's crystal glows blindingly white, indicating unparalleled physical and magical capabilities, including the ability to use all levels of magic and complete immunity to all forms of attack. This overwhelming power causes her to faint. She later learns from a divine voice that her wish for an invincible body was granted to an extreme degree, making her effectively invincible.
Upon waking, Mary is informed that her power shattered the crystal artifact and that her father, enraged by the potential danger to her, stormed the temple. Mary, fearing her power and the potential for rejection, confides in Tute about her "cheat abilities." Tute, initially overwhelmed, pledges her loyalty. Mary decides she must learn to control her power and requests martial arts training. Her father agrees, arranging for her to train with his old comrade, Count Elixil, and his son, Zach, who becomes Mary's sparring partner.
During training, Mary discovers her immense strength makes it difficult to control her movements and avoid damaging things. She easily defeats Zach, who is arrogant about his martial prowess. Meanwhile, Mary receives a summons to the royal palace. Fearing she has offended the First Prince, Rayforth, whom she met briefly during the Oracle Ceremony and accidentally caused to stumble, she prepares a formal apology.
Upon arriving at the palace, Mary is ambushed by a magical water trap. Seizing the opportunity to avoid meeting the prince, she uses the incident as an excuse to leave, much to the dismay of her father, who learns of the incident and heads to the palace in a rage.
