In the summer of 1907, the 40th year of the Meiji era, Japan is a nation in flux, where traditional customs clash with the rapid adoption of Western technology. In the Fushimi district of Kyoto, fifteen-year-old Inako Momokawa lives as the second daughter of a sake brewing family. Plagued by a seemingly endless streak of bad luck and incompetence, she is frequently scolded by her father and finds her only solace in fervent prayers to the gods at the local Fushimi Inari Shrine. Her life takes an unexpected turn when she meets Kihachi Sakamoto, a bold and free-spirited boy of the same age who works at his uncle's appliance repair shop. Kihachi is her complete opposite, rejecting faith in the unseen and loudly proclaiming that the future belongs not to deities, but to the new age of electricity.

As Inako struggles to live up to her family's expectations, she is suddenly confronted with a unilateral decision by her father to arrange her marriage. Feeling trapped and worthless, she resigns herself to this fate. However, Kihachi refuses to let her give up, breaking her out of her locked house and offering a radical solution to stop the wedding. The only way out is to find a mysterious book known as the Electrical Catalog, a notebook filled with predictions about electrical inventions that Kihachi wrote as a child. The book was taken by his older brother, Seiroku, who has since vanished without a trace.

Together, Kihachi and Inako embark on a journey across the Kyoto and Shiga prefectures to find the lost catalog. Their search forces Inako to confront her own lack of confidence while Kihachi is driven to reclaim a piece of his forgotten dreams and uncover the truth about his brother’s disappearance. The secret hidden within the vanished catalog holds the potential to realize the dreams they once had.

The story delves into the past, revealing that on New Year's Day 1901, a nine-year-old Kihachi was inspired by his older brother Seiroku to begin writing the Electrical Catalog. Two years later, Seiroku took Kihachi to the Fifth National Industrial Exposition in Osaka to spark his imagination with unfamiliar electrical wonders. It was there that Seiroku mysteriously abandoned the young Kihachi, disappearing and leaving him with only the notebook that would become the center of their quest years later. In the present, their search puts them in the path of other key figures, including Inako's older sister Noriko and her war veteran fiancé Kengo Riku, as well as the wealthy heir Yosuke Mizoe, whose recognition of the Electrical Catalog’s name suggests he knows more about its significance than he lets on.