"Captain Ken" is a science fiction manga series set on Mars, where humanity has established colonies and adapted to the harsh environment. The story centers on Ken, a young boy who becomes a symbol of resistance against the oppressive Martian government. Ken's journey begins when he discovers a hidden spaceship, which he names "Captain Ken," and uses it to fight for justice and freedom. The Martian government, led by the authoritarian General Gurumen, enforces strict control over the colonies, exploiting the settlers and suppressing any dissent. Ken's actions inspire the oppressed colonists to rise up against their rulers.

The narrative explores themes of rebellion, heroism, and the struggle for autonomy. Ken is joined by a diverse group of allies, including Miya, a brave and resourceful girl, and Dr. Kettel, a scientist who aids Ken in his fight. Together, they navigate the challenges of Martian society, uncovering secrets about the planet's history and the true intentions of the ruling elite. The series blends action, adventure, and political intrigue, with Ken's leadership and determination driving the plot forward. The conflicts escalate as Ken and his allies face increasingly formidable adversaries, culminating in a climactic battle for the future of Mars. The story balances personal growth with larger societal struggles, creating a compelling tale of courage and resilience in the face of tyranny.