"UFO Ultramaiden Valkyrie" is a romantic comedy anime series with elements of science fiction and fantasy. The story centers on Kazuto Tokino, a young man who works at a bathhouse and dreams of becoming a professional racer. His life takes an unexpected turn when a mysterious spaceship crashes into the bathhouse, revealing Valkyrie, a princess from the planet Valhalla. Valkyrie is on a mission to find her soulmate, as her planet's tradition dictates that she must marry to secure peace. However, during the crash, Valkyrie's soul splits into two separate entities: her mature, responsible self and a younger, more childlike version named Valkyrie-chan.

Kazuto becomes entangled in Valkyrie's quest, as she believes he may be her destined partner. The series explores their evolving relationship, as well as the challenges posed by the presence of Valkyrie-chan, who represents Valkyrie's innocent and carefree side. The dynamic between the three characters forms the core of the narrative, with Kazuto often caught between the two versions of Valkyrie.

The story also introduces other characters from Valhalla, including Valkyrie's loyal attendants, Hydra and Sanada, who assist her in her mission. Additionally, rival suitors and antagonists from Valhalla complicate Valkyrie's efforts to find her soulmate. The series blends comedic moments with heartfelt scenes, as Kazuto and Valkyrie navigate their feelings for each other while dealing with the consequences of her split soul.

As the plot progresses, themes of love, identity, and self-discovery are explored, with Valkyrie's dual nature serving as a metaphor for her internal conflict and growth. The series incorporates elements of space opera, with battles and interstellar politics occasionally intersecting with the more personal and comedic aspects of the story. Ultimately, "UFO Ultramaiden Valkyrie" balances its fantastical premise with a focus on character relationships, creating a narrative that is both whimsical and emotionally engaging.