After stumbling upon giant robot remnants from the sky, Nobita and Doraemon venture into a mirror world to construct the formidable Zandacross. As they uncover its potential as a perilous weapon, they guard this secret closely. The arrival of enigmatic Lilulu adds a twist as she demands Zandacross for an impending invasion, despite her reluctance to harm Earth. United with Doraemon, the group bands together to thwart the looming robotic army invasion, realizing that Lilulu holds the key to halting the chaos.