"Kinnikuman: Kessen! Shichinin no Seigi Chōjin vs. Uchū Nobushi" is a direct continuation of the "Kinnikuman" series, focusing on the ongoing battles between the Justice Chojin and the Space Nobushi. The narrative centers on Kinnikuman, a clumsy yet determined hero, and his allies, the Seven Justice Chojin, as they face a new threat from the Space Nobushi, a group of powerful alien warriors seeking to dominate the universe. The story unfolds as the Justice Chojin are summoned to defend Earth and the Chojin world from the Space Nobushi's invasion.

The conflict escalates when the Space Nobushi, led by the formidable Akuma Shogun, challenge the Justice Chojin to a series of high-stakes battles. Each member of the Seven Justice Chojin, including characters like Terryman, Robin Mask, and Ramenman, is pitted against a specific Space Nobushi warrior in one-on-one matches. These battles are not only tests of strength and skill but also of resolve and loyalty, as the Justice Chojin must overcome their personal struggles and past traumas to protect their world.

Kinnikuman, despite his initial insecurities and self-doubt, emerges as a key figure in the fight against the Space Nobushi. His growth as a warrior and leader is a central theme, as he learns to harness his latent abilities and inspire his teammates. The series delves into the backstories of both the Justice Chojin and the Space Nobushi, revealing motivations and conflicts that add depth to the characters and their interactions.

The climax of the series features a decisive showdown between Kinnikuman and Akuma Shogun, with the fate of the Chojin world hanging in the balance. The resolution of this conflict underscores themes of perseverance, unity, and the enduring power of justice. Throughout the series, the narrative maintains a balance between intense action sequences and moments of character development, ensuring a cohesive and engaging storyline.