The film opens with Doraemon and his friends testing a futuristic game device from the future. They attempt a high-speed race, but Gian and Suneo Honegawa surge ahead, unintentionally sending Nobita Nobi, Doraemon, and Shizuka Minamoto back to Nobita's room. In the aftermath, Nobita asks for another gadget, and Doraemon grants the Gravity Modifier, which briefly renders the room weightless. That playful situation spirals when the device is destroyed, tossing the room into disarray and trapping Gian and Suneo inside.
As the group tidies up, they discover the game was discarded by Nobita’s mother and vanished into the trash. Using the Time Camera, Doraemon witnesses a strange light lifting the game away toward a spaceship, and a glowing rock collapses into their hands at the crash site. Intrigued, Doraemon, Nobita Nobi, and Shizuka Minamoto climb aboard the Space Exploration Boat to pursue the mystery, chasing a path through a perilous wormhole storm.
The chase leads to a spaceship where Gian and Suneo have been taken inside. The ship’s crew confronts the newcomers, insisting they belong to the vessel’s mission and locking the intruders in the same room from before. Soon, the ship begins to falter and must land on a barren planet, where the group escapes into a landscape marked by jagged rocks and enormous metallic spiders. The spiders trap the ship in their webs, threatening to seal it off forever. In a decisive move, Doraemon persuades Gian to inflate a huge Hamelin Pipe, scattering the spiders and clearing the way so the ship can be freed.
Once the newcomers are understood as allies, the humans on board introduce themselves as Lian, Log, Freya, and Gorogoro. They are returning to their mothership after a mission to scout for a habitable, uninhabited planet. Their plan is to repair a malfunctioning warp device and resume their voyage home. However, disaster strikes again when the warp system falters, forcing a crash landing on a foggy world. The group awakens to a dreamlike sequence: Nobita blinks in response to a glowing stone, only to discover a desolate landscape inhabited by towering treelike creatures. Realizing they are dreaming, Doraemon uses the Faraway Wake Up Clock to rouse everyone, and Lian’s crew quickly rescues them despite a challenging exit through a stubborn ship door.
The voyage resumes through a space field littered with debris, but a swarm of “live meteors” latches onto the ship and drains its power. A surprise missile saves them and deposits the party at a secret base, where they meet Liebert, who turns out to be Lian’s father. Liebert warns of Angolmois, a cloaked figure intent on conquering Earth, while Freya is revealed to be a spy. The others are imprisoned, and the group must improvise a plan to escape.
Using an underground submarine, Doraemon, Nobita, Shizuka, Gian, and Suneo escape and sprint toward Lian’s ship while fending off Angolmois’s robot soldiers. Freya hesitates at first but ultimately joins the resistance, following Lian’s urging. With the mothership looming and its engines failing again, the leaders debate how to handle Angolmois’s threat. They call upon their “god”—a colossal, radiant tree—believing it can do something extraordinary. The glowing seed Nobita discovered on Earth is revealed to be one of the tree’s seeds, which Lian accidentally dropped. A vision of Lian’s late mother appears through the seed when he prays, guiding him to rescue his father from Angolmois’s control.
The group commandeers Doraemon’s ship and, aided by Lian and Freya, launches a coordinated counterattack that brings Angolmois’s fleet to heel. They disable the enemy forces with a Nendoron-powered transformation, turning the key control rod to clay and rendering the invaders helpless. Angolmois’s lair is exposed as a spaceship, and the hero crew boards to confront him. Liebert betrays Angolmois’s control and turns his weapons against him, revealing Angolmois to be a robot in disguise.
With the mothership now in danger, the team enacts a dramatic rescue. They deploy a Reverse Cloak and illuminate the hull with the Big Light, steering the fleet away from catastrophe. Angolmois, who has rebuilt himself from garbage into a new form, is trapped when a door seals him in; Doraemon freezes him with the Coagulation Light and hurls him into a black hole.
The inhabitants of the mothership celebrate their survival as Lian’s group returns Doraemon and friends home. Lian vows to search for another planet where his people can thrive, and the film closes with a echo of the fog-planet scene—this time with a sense of resolution and hope rather than uncertainty.
