As Nobita dozes off, the ground beneath him begins to shake, as if an earthquake were occurring within his own bedroom. Unbeknownst to him, a petite rabbit hailing from an alternate universe by the name of Chamii uses a hammer to pry open the dimensional door, allowing her to enter Nobita's quarters via the floorboards. Upon waking up, Nobita catches wind of someone stealthily pilfering food from his kitchen's refrigerator; it is revealed to be Chamii, who is promptly apprehended by Nobita and Doraemon. Wielding knowledge of a secret passageway that leads through the floor and into her spaceship, Chamii leads her captors on a journey that lands them on the Koya Koya Planet. There, they are introduced to Roppuru, a young boy.