A 40-year-old protagonist named Dereto has dedicated his life to blacksmithing in a small town, but one day, he is suddenly expelled by his fellow guild members. With nowhere to go, he remembers a letter he received from a young girl for whom he once crafted a “toy weapon” and decides to head to the royal capital. Upon arrival, he discovers that the “toy weapon” he had made has evolved into a legendary weapon, and the girl has become a national hero! His life turns around from being an unemployed middle-aged man to being celebrated as the hero who crafted a legendary weapon. To his surprise, he reunites with the colleagues who had cast him out in an unexpected way, eventually taking them on as his apprentices!