Grand Doll is a science fiction story centered on the invasion of Earth, featuring a boy's struggle against extraterrestrial invaders. As part of their scheme to conquer the planet, the aliens dispatch a doll capable of transforming into a human to Earth. Utsuki Tetsuo, a junior high school student commonly known as Tecchin, is an ordinary boy lacking strong willpower or the ability to assert himself. One day, while walking home from school, he discovers a girl's corpse on the street. As he heads to the police to report the incident, the body vanishes. In its place, he finds a peculiar doll. Tetsuo takes the doll home and fixes its broken part. The doll then instantly transforms into the girl who had appeared dead. It informs him that it is a "Grand doll," and that Tetsuo is one as well. A Grand doll resembles a standard doll at first glance, but rubbing its neck causes it to transform into a human or a horse. Scratching the neck reverts it back to a doll. The aliens from outer space are the ones distributing Grand dolls across Earth. This action is actually part of their plot to invade the planet. Upon learning this, Tetsuo resolves to fight the invaders with the assistance of his father, a newspaper reporter, and his friend Yoko, despite his fear that he might also be a Grand doll.