"Prince Planet" is a science fiction anime series set in a futuristic universe where Earth is part of the United Worlds of the Galaxy, a coalition of planets striving for peace and cooperation. The Galactic Council, overseeing this alliance, selects a representative from each member planet to compete in a series of tests to determine the worthiness of their world. The winner earns the title of Prince Planet and the responsibility of maintaining galactic harmony.

The protagonist is Prince Planet, a young boy from the planet Radion, who is sent to Earth as its representative. Disguised as a human named Bobby, he blends into Earth's society while secretly fulfilling his mission. Prince Planet possesses a medallion that grants him superhuman abilities, including enhanced strength, speed, and the power to transform into a more powerful, armored form. The medallion also serves as a communication device with the Galactic Council.

Throughout the series, Prince Planet faces various challenges, both physical and moral, as he competes against representatives from other planets. These challenges often involve thwarting the schemes of rival competitors, particularly those from the planet Zatonia, whose representatives seek to undermine the competition and seize control of the galaxy. The Zatonians, led by the villainous Duke of Zatonia, frequently employ deceit, sabotage, and advanced technology to gain an unfair advantage.

Prince Planet is aided by a group of Earth allies, including Diana, a resourceful and courageous girl who becomes his closest confidante, and Dan, a loyal friend who provides support and comic relief. Together, they navigate the complexities of the competition while defending Earth from external threats. The series explores themes of justice, integrity, and the importance of cooperation, as Prince Planet consistently demonstrates his commitment to fairness and the greater good.

The narrative is episodic, with each episode presenting a new challenge or adversary. However, an overarching plotline ties the series together, culminating in a final confrontation with the forces of Zatonia. Prince Planet's journey is not only a test of his abilities but also a reflection of his growth as a leader and his dedication to the ideals of the United Worlds of the Galaxy. The series balances action, adventure, and moral lessons, making it a classic example of early science fiction anime.