"Kitarō Tanjō: Gegege no Nazo" is a 2008 anime film that serves as a prequel to the long-running "GeGeGe no Kitarō" series, exploring the origins of the titular character, Kitarō, and his connection to the supernatural world. The story is set in a world where humans and yokai (supernatural beings) coexist, often in tension. The narrative begins with the tragic death of Kitarō's father, Medama Oyaji, a yokai who sacrifices himself to protect his unborn son. Kitarō is born as a half-human, half-yokai child, inheriting his father's supernatural abilities and a deep sense of justice.

The plot centers on Kitarō's early years, as he grows up isolated and misunderstood due to his hybrid nature. His mother, a human, struggles to raise him while grappling with the fear and prejudice of their village. Kitarō's journey begins when he encounters a group of yokai who recognize his potential and guide him to embrace his heritage. Among them is Nezumi Otoko, a mischievous rat yokai who becomes both an ally and a source of comic relief. Kitarō also meets other iconic characters from the series, such as Neko Musume, a cat yokai with a tragic past, and Sunakake Baba, a sand-throwing yokai who aids him in his quest.

The central conflict arises when a powerful and malevolent yokai named Nurarihyon seeks to dominate both the human and yokai worlds. Nurarihyon's schemes threaten the fragile balance between the two realms, and Kitarō is drawn into the struggle to stop him. Along the way, Kitarō learns about his father's legacy and the importance of protecting the coexistence of humans and yokai. The film delves into themes of identity, acceptance, and the struggle to bridge two worlds, as Kitarō grapples with his dual nature and the responsibilities it entails.

The narrative is driven by Kitarō's growth from a lonely, uncertain child into a confident hero who embraces his role as a mediator between humans and yokai. The film also explores the origins of his iconic tools, such as the Chinki Chinki Pon and his enchanted vest, which become symbols of his mission to maintain harmony. By the end, Kitarō emerges as a figure of hope, embodying the ideals of his father and setting the stage for his future adventures in the "GeGeGe no Kitarō" series. The story is a blend of supernatural action, emotional depth, and folklore-inspired storytelling, offering a compelling introduction to the beloved character and his world.