Summer vacation comes to Graviton High School, and the girls can't wait to get out of school! They each have big plans for vacation. A-ko, a high school student with incredible superpowers, vows to lose a few inches off her waistline. The wealthy and beautiful B-ko will not rest until she can get A-ko out of the way, and have the adorable C-ko all to herself. And C-ko happily makes a list of all the cool things she'll buy during vacation.

B-ko starts working on her summer plans right away by designing a giant anti-A-ko robot. But her father, head of the powerful Daitokuji Financial Group, has other palns for his daughter's designs. By programming the robot to attack the alien spacecraft that has landed in Graviton City, he hopes to gain control of the ship's advanced technological secrets for his company!