The protagonist, a Japanese woman exhausted from overwork, is abruptly transported to another world and finds herself reborn as an Ancient Dragon. Initially overwhelmed and frustrated by her new form and the sudden transmigration, she struggles with her immense size and the constant attacks from various monsters. Her anger manifests as blue-white flames from her mouth, and her movements inadvertently cause destruction, shattering rocks and felling trees. She discovers she can use magic, creating a barrier and a shield to defend herself from the relentless monsters.
Upon arriving in this new world, she is greeted by a mysterious, fluffy white creature resembling a dandelion puff, which calls itself a "fluffball." This entity explains that the world's balance is collapsing due to the absence of a supreme being for the past five hundred years. The protagonist, possessing a soul comparable to the strongest of ancient species, has been chosen to restore this balance. She vehemently refuses this proposition, preferring her human life and familiar world. The fluffball, however, is persistent, revealing that she has been asleep for a year in her original world and that her transmigration is necessary.
Despite her protests, the fluffball forcibly initiates the transmigration process, promising a hundredfold increase in her reincarnation benefits as compensation for her anger. The protagonist, still clinging to the hope of returning to her world, is then thrust into the new world.
Upon waking in her dragon form, she finds herself in a dark, dense forest filled with monsters. She quickly adapts, learning to deal with the smaller, bothersome monsters and utilizing her newfound abilities. She discovers her status screen, revealing her as an Ancient Dragon with maxed-out stats and powerful skills, including "Change" (allowing her to transform into human form), "Skill Creation," and "Knowledge of the Spring." The "Knowledge of the Spring" skill proves invaluable, providing her with information about the world, its inhabitants, and its customs, including the name of the world, "Astrea," and its sole goddess, "Asteria."
She learns that monster meat is the primary source of food in Astrea, and that animals are primarily used for dairy products. She also discovers a beautiful, pristine lake and a cave suitable for her dragon form. With the help of "Knowledge of the Spring," she begins to explore her new surroundings, planning to gather information before venturing into towns or other continents. She also reflects on the fluffball's true nature and its role in her transmigration, harboring a strong desire for revenge. The narrative ends with her preparing to explore the world, armed with her immense power and the knowledge provided by her new skill.