The live-action film Red Shadow: Akakage is set in 16th century Japan during the tumultuous Warring States period. The story follows a trio of young ninja known as the Shadow Clan, who serve the powerful warlord Togo Hidenobu. The clan’s original purpose, passed down through generations, is to work in secret to bring about a peaceful world of light. The three remaining successors are Akakage, the skilled swordsman and protagonist; his best friend Aokage, who is more prone to bumbling and comedy; and Asuka, a capable female ninja who shares a deep, unspoken romantic connection with both young men.

The trio is trained by the elderly Shirokage, the White Shadow and their leader. As the narrative begins, the young ninjas find their faith in their mission wavering. They begin to feel a disconnect between the idealistic lessons of their clan and the pragmatic, often ruthless orders they receive from Lord Togo. The plot takes a sharp and unexpected turn when Asuka is killed during a mission. Her death devastates both young men; Aokage becomes despondent and abandons his life as a ninja, while a disillusioned Akakage also questions his path.

Left on his own, Akakage is ordered to assassinate Princess Koto, the ruler of a rival domain. However, upon discovering that the princess is being targeted by a traitorous chamberlain who seeks to seize her castle and plunge the nation into civil war, Akakage disobeys his orders. Instead of killing her, he chooses to protect her and fight against the chamberlain’s forces. The latter half of the film follows this mission as Akakage, aided by the sudden return of Aokage and Shirokage, helps Princess Koto reclaim her castle, defeat the usurper, and avert a larger war. A quiet romance develops between the ninja and the princess, but their different stations in life mean it can never be realized. After completing their mission, Akakage and his companions disappear, and the film ends with them paying respects at Asuka's grave.

Unlike the original 1960s source material, which featured the heroes battling giant monsters (daikaiju) with high-tech gadgets, this 2001 live-action adaptation is a loose remake that reimagines the characters and story from scratch. It is a stylistic homage to and a playful deconstruction of the ninja and samurai genres, blending action, modern humor, anachronistic elements, and a sudden tragic turn that fundamentally alters the lighthearted tone of its first half.