"Kinnikuman: Gyakushū! Uchū Kakure Chōjin" is a direct sequel to the original "Kinnikuman" series, continuing the adventures of the titular character, Suguru Kinniku, also known as Kinnikuman. The story picks up after the conclusion of the 42nd Superhuman World War, where Kinnikuman emerged victorious, solidifying his status as a hero. However, peace is short-lived as a new threat emerges from the depths of space. A group of powerful and mysterious Chōjin (superhuman wrestlers) known as the Uchū Kakure Chōjin (Space Hidden Chōjin) arrives on Earth, challenging Kinnikuman and his allies to a series of high-stakes wrestling matches. These extraterrestrial warriors possess unique abilities and are determined to prove their superiority over Earth's Chōjin.

The narrative revolves around Kinnikuman and his friends, including Terryman, Robin Mask, and Ramenman, as they face off against the Uchū Kakure Chōjin in a tournament-style format. Each match is a battle of wits, strength, and strategy, with the fate of Earth hanging in the balance. The Uchū Kakure Chōjin are led by the enigmatic and formidable Akuma Shogun, who harbors a deep-seated grudge against Kinnikuman and seeks to exact revenge for past grievances. As the tournament progresses, Kinnikuman and his allies uncover the true motives behind the Uchū Kakure Chōjin's invasion, revealing a complex web of betrayal, rivalry, and redemption.

Key characters include Kinnikuman, whose growth as a hero is tested against increasingly powerful opponents; Terryman, the loyal and steadfast friend who provides unwavering support; Robin Mask, the noble and disciplined warrior with a tragic past; and Ramenman, the reformed villain turned ally who brings a unique perspective to the team. The Uchū Kakure Chōjin are equally compelling, with each member showcasing distinct personalities and abilities, such as the cunning and manipulative Brocken Jr., the honorable but conflicted Warsman, and the relentless and brutal Buffaloman.

The series maintains a balance between intense wrestling action and character-driven drama, exploring themes of friendship, perseverance, and the struggle between good and evil. As the battles escalate, Kinnikuman and his allies must confront their own limitations and insecurities, pushing themselves to new heights to protect their world. The climax of the series sees Kinnikuman facing off against Akuma Shogun in a final, decisive match that will determine the fate of Earth and the legacy of the Chōjin. Through its engaging storyline and memorable characters, "Kinnikuman: Gyakushū! Uchū Kakure Chōjin" delivers a compelling continuation of the Kinnikuman saga, blending action, humor, and heartfelt moments in a way that resonates with fans of the franchise.