Sixth-grader Yuri Otani is chosen by her classmates to serve as one of the three members of Elementary School 9's "Alien Party," joining fellow "Alien Fighters" Kumi Kawamura and Kasumi Tomine. Their primary duty is to capture, rather than kill, any aliens that invade the school grounds. They are assisted by advisor Ms. Megumi Hisakawa and symbiotic aliens known as "Borg," which attach to their hosts' heads to shield them from danger. Yuri's main reason for disliking her role in the Alien Party is her intense fear of aliens. If she does not faint upon seeing them, her terror leaves her frozen, preventing her from completing her tasks. Consequently, Kumi, Kasumi, and Yuri's Borg must compensate for her inaction. Ms. Hisakawa informs the girls that a stronger fusion with their Borgs will make them more effective in their duties. However, could there be a hidden motive behind the Alien Party's existence and the bond between the girls and the Borgs?