Grand Doll is an enthralling sci-fi tale that delves into the extraterrestrial invasion of Earth, following a young boy's heroic journey against the invading beings. The aliens have devised a nefarious plan to vanquish the planet by dispatching a doll with shape-shifting abilities, capable of turning into a human. Utsuki Tetsuo, fondly called Tecchin, is a regular middle-school pupil who lacks self-assurance. One eventful day, while he chances upon a lifeless girl on the street, he stumbles upon a strange doll in her place after informing the authorities.
Tetsuo mends the doll, and it transforms into a human who introduces herself as the "Grand doll." Tetsuo discovers that he, too, is a Grand doll, and the extraterrestrials are using these dolls to infiltrate Earth as part of their invasion. Although he fears becoming a Grand doll, Tetsuo partners with his father, a newspaper journalist, and his friend Yoko, to oppose the alien intruders.
