"Eiga Crayon Shin-chan Shūrai! Uchūjin Shiriri" is a feature-length anime film in the Crayon Shin-chan franchise. The narrative centers on Shinnosuke "Shin" Nohara, a mischievous and energetic five-year-old boy, and his family, who become entangled in an extraterrestrial conflict. The story begins when an alien named Shiriri crash-lands near Shin's home in Kasukabe. Shiriri, a small, cute alien, is pursued by a powerful and menacing alien force known as the Dark Guard, who seek to capture her for her unique abilities. Shiriri's presence disrupts the Nohara family's daily life, as she inadvertently causes chaos with her alien powers, including teleportation and energy manipulation.

As the Dark Guard closes in, Shin and his family, along with his friends, must protect Shiriri and help her return to her home planet. The Nohara family, including Shin's parents, Hiroshi and Misae, and his baby sister, Himawari, play pivotal roles in the unfolding events. Hiroshi and Misae, though initially skeptical of Shiriri's origins, gradually come to understand the gravity of the situation and join forces with Shin to safeguard the alien. The story also introduces new characters, such as Shiriri's allies from her home world, who provide additional context about the ongoing interstellar conflict.

The plot escalates as the Dark Guard launches a full-scale invasion of Earth, threatening not only Shiriri but also the entire planet. Shin and his friends, including Kazama, Nene, and Masao, band together to devise a plan to repel the invaders. The film balances humor, action, and heartfelt moments, characteristic of the Crayon Shin-chan series, while exploring themes of friendship, family, and courage. The climax involves a high-stakes battle where Shin and his allies use their ingenuity and teamwork to outwit the Dark Guard and ensure Shiriri's safe return to her world. The resolution ties up the narrative threads, leaving the Nohara family to reflect on their extraordinary adventure while returning to their everyday lives.