Following a dramatic event that stranded Captain Napolipolita's ship atop Graviton City, A-Ko and her friends embark on a summer getaway. As A-Ko contemplates shedding some pounds and B-Ko hatches a plan to outsmart her fiery-haired rival for the affections of C-Ko, Napolipolita and Spy-D grapple with intense homesickness, yearning for a way back to their homeworld. Concurrently, Hikari Daitokuji, B-Ko's father and the head of Daitokuji Financial Group, equips the local military with cutting-edge mecha to seize Napolipolita's vessel and acquire its advanced technology.