"Eiga Doraemon: Nobita no Chikyū Symphony" is a feature-length anime film centered on the adventures of Nobita Nobi, his robotic cat Doraemon, and their friends. The narrative begins with Nobita struggling with his usual academic and personal challenges, prompting Doraemon to introduce a futuristic gadget to help him. This gadget, a music composition device, allows Nobita to create symphonies effortlessly. Intrigued by its potential, Nobita uses it to compose a piece that unexpectedly resonates with an alien civilization.

The alien civilization, known as the Planet Symphonia, is facing a crisis. Their world thrives on music, which sustains their environment and culture. However, their ability to create music is diminishing, threatening their survival. Upon hearing Nobita’s composition, the aliens recognize its unique quality and invite Nobita and his friends—Doraemon, Shizuka, Gian, and Suneo—to their planet to help restore their musical harmony.

Upon arriving on Planet Symphonia, the group discovers a society deeply connected to music, where every aspect of life is influenced by melodies and rhythms. The aliens explain that their planet’s core, the "Music Stone," is losing its power, and only a new, original symphony can rejuvenate it. Nobita, despite his initial lack of confidence, is tasked with composing this symphony, as his earlier work demonstrated a rare emotional depth.

As Nobita and his friends work on the symphony, they encounter various challenges. The planet’s environment begins to deteriorate further, and they face opposition from individuals who doubt their abilities. Additionally, the group learns about the history of Planet Symphonia and the importance of preserving its musical heritage. Through teamwork, creativity, and perseverance, Nobita and his friends strive to complete the symphony, hoping to save the alien civilization.

The film explores themes of friendship, self-discovery, and the universal power of music. Nobita’s journey from a hesitant and insecure individual to someone who embraces his potential forms the emotional core of the story. The interactions between the characters, their growth, and their efforts to understand and connect with the alien culture drive the narrative forward. The climax centers on the performance of the symphony, which becomes a pivotal moment for both the characters and the fate of Planet Symphonia.