"Nihon Tanjō" is a historical anime series that explores the origins and formation of Japan as a nation, blending mythology, history, and cultural elements. The narrative is structured around the legendary figures and events that shaped early Japanese civilization, drawing heavily from the Kojiki and Nihon Shoki, two of Japan's oldest historical texts. The story begins with the creation myths, depicting the divine siblings Izanagi and Izanami, who are tasked with forming the islands of Japan. Their actions set the stage for the emergence of the Japanese archipelago and the birth of its deities.

The central focus shifts to the descendants of these deities, particularly Amaterasu, the sun goddess, and her brother Susanoo, the storm god. Their tumultuous relationship and the conflicts arising from their actions drive much of the early narrative. Amaterasu's role as a symbol of light and order contrasts with Susanoo's chaotic nature, creating a dynamic interplay that reflects the balance of forces in the natural world. The series delves into the myth of Amaterasu's retreat into a cave, plunging the world into darkness, and her eventual return, which restores harmony.

As the story progresses, it transitions from mythological tales to more grounded historical events, focusing on the lineage of Amaterasu's descendants, who become the first emperors of Japan. The series highlights key figures such as Emperor Jimmu, traditionally regarded as Japan's first emperor, and his journey to unify the land. The narrative emphasizes the challenges faced by early leaders, including territorial disputes, alliances with local clans, and the establishment of a centralized authority.

The anime also incorporates the influence of Shinto beliefs and practices, portraying rituals, ceremonies, and the reverence for kami (spirits) as integral to the cultural and political development of early Japan. The interplay between humans and deities is a recurring theme, with characters often seeking divine guidance or intervention to overcome obstacles.

Throughout the series, the animation and storytelling maintain a balance between mythological grandeur and historical authenticity, presenting a cohesive account of Japan's foundational myths and early history. The characters are depicted with distinct personalities and motivations, reflecting their roles as both legendary figures and symbolic representations of natural and cultural forces. The series concludes with the establishment of the Yamato dynasty, marking the beginning of a unified Japanese state and the enduring legacy of its mythological origins.