All alone in the city of the future

what happens

Nobita travels to the 22nd century after Doraemon leaves, only to discover a seemingly deserted futuristic city where he encounters anti-gravity tech, strange shops, and what he believes is an alien invasion. He meets Sewashi, who explains everything is actually part of a 3D game called “Intruders,” not a real crisis. Embarrassed but relieved, Nobita learns Doraemon was only temporarily away for repairs. Doraemon later returns, and they go back to the 20th century together, where Nobita immediately wants to keep playing the game.