In the 21st century mankind was on the brink of destruction. Through genetic engineering however they eradicated such feelings as love and the desire for power. Since women are naturally less agressive than men, women to man ratio was set to 9:1. Now people are engineered to have skills that others view as being necessary. There is a giant ring that now orbits the earth, that sits there and relays information back to an alien race that sent it. Now a team of five women will try to eradicate the alien threat. (Source: ANN)

The story is set in Nagasaki prefecture in Minami Shimabara city, the fabled origin of the Shimabara Rebellion that sent shockwaves through all of Japan in the early Edo period. It is also where a third-year junior high school student named Shirou spends his days with his school friends. One summer day, Shirou's older childhood friend Akane returns to Minami Shimabara from Tokyo. Shirou and Akane take a stroll around Minami Shimabara with another longtime friend, Tokiya. While these friends are dealing with nostalgia and more complex feelings, a mysterious creature named Goron suddenly appears before them. This encounter with a mere little creature causes great events to unfold once more in this city...

The peaceful days turn out to be short-lived as the shadow of another Selector Battle looms large. Kiyoi Mizushima is the first to notice that things are amiss, and she makes her move to put an end to the cycle of darkness.The Battle this time includes a new card, "Key," and has been set up with rules different than before. With both the mastermind and their motive shrouded in mystery, the darkness grows ever deeper and more menacing. Suzuko Homura, Chinatsu Morishita, Hanna Mikage, Ruuko Kominato, Yuzuki Kurebayashi, Hitoe Uemura, and Akira Aoi, the Selectors gather once again. (Source: ANN)