In 2038, a white light descended upon central Tokyo, erasing the memories of more than one million people. The cause of this tragic event remains undetermined, and no cure has been found. The government established a separate city beneath Tokyo to house and care for the victims, labeling them as "KIDz." Regardless of their actual age, they behave like children and must be retaught everything they once knew. Noa Ikurumi, who lives within this isolated society, takes each day as it comes, dreaming of the day he will finally be allowed to return to the outside world. However, Noa's life is set to change drastically once again when he is taken hostage by a terrorist who possesses surprising information regarding his identity...