"Ultra Nyan: Hoshizora Kara Maiorita Fushigi Neko" is a two-part OVA series that blends science fiction, comedy, and adventure. The story centers on a mysterious alien cat named Ultra Nyan, who arrives on Earth from outer space. Ultra Nyan possesses extraordinary abilities, including the power to transform into a giant, super-powered feline capable of defending the planet from extraterrestrial threats. The narrative unfolds as Ultra Nyan teams up with a young girl named Hikaru and her family, who discover the cat after it crash-lands near their home.

The plot is driven by Ultra Nyan's mission to protect Earth from an alien invader named Garugaru, who seeks to conquer the planet. Garugaru, a comically inept yet persistent antagonist, deploys various robotic monsters and schemes to achieve his goal. Ultra Nyan, with the help of Hikaru and her family, confronts these threats, often using humor and ingenuity to outwit the enemy. The series balances lighthearted moments with action-packed sequences, as Ultra Nyan's transformations and battles against Garugaru's forces take center stage.

The main characters include Ultra Nyan, whose playful and mischievous personality contrasts with its heroic capabilities; Hikaru, a spirited and curious girl who forms a close bond with the alien cat; and Hikaru's family, who provide support and comedic relief throughout the story. Garugaru serves as the primary antagonist, with his exaggerated villainy and frequent failures adding a comedic tone to the conflict. The narrative emphasizes themes of friendship, teamwork, and the triumph of good over evil, all while maintaining a whimsical and family-friendly atmosphere. The OVA's concise runtime ensures a fast-paced and entertaining experience, with a focus on action, humor, and the endearing relationship between Ultra Nyan and its human companions.