Hajime Ichinose's everyday existence is turned upside down when a transcendent being named J.J Robinson delivers her a little book called NOTE—a device that changes her into one of Tachikawa City's renowned guardians, the Gatchaman. Sugane Tachibana, a fellow Gatchaman, brings Hajime to their headquarters of operations, where Paiman, the panda-like extraterrestrial commander of the Gatchaman, discloses their purpose: to destroy aliens that represent a threat to mankind. These existential dangers, known as MESS, are getting increasingly destructive, killing everything they come into contact with. It is now up to the Gatchaman and their new recruit to stop them before the planet is destroyed.