Project A-ko: Grey Side/Blue Side

Project A-ko: Grey Side/Blue Side is last movie in the Project A-ko series. This two-part story takes place in an alternate universe, where counterparts of our heroines find themselves in the middle of a space opera. In this world, A-ko and B-ko are bounty-hunter partners who hunt giant tortoises on a sand planet. When C-ko is kidnapped by a gang of space pirates, A-ko and B-ko set off to rescue her—thinking only of the reward money offered by her wealthy father. Aided by a pint-sized Galactic Police Officer named Maruten, the girls discover that C-ko's abduction is part of a much larger scheme. Gail, the charismatic leader of the space pirates, intends to use C-ko's body as a host for the spirit of Xena, a long-dead sorceress. Although Gail believes that Xena will "purify" the universe, he is oblivious to her true motive—to annihilate all universes and create a new one in which she is the absolute ruler.

The final showdown occurs in the Talho sector, where Xena begins to merge all existing universes into one. This features A-ko and B-ko fighting each other in a variety of different eras and locations, including the climatic battle of the first movie. This seems to suggest that the two are always destined to battle.

The audience is also treated to what could be a brief glimpse of A-ko and B-ko back on planet Earth, in which the girls graduate from Graviton High and continue their rivalry for Kei in the workplace.

In the end, the universe is saved, Maruten takes all of the credit, and A-ko and B-ko are left as broke and short-tempered as they began.