Without warning in the year 2050, an alien race known only as the Inbit arrive, invade and successfully conquer the Earth. Years later and despite brutal past failures, the inhabitants of Mars Colony send out yet another desperate Liberation Force to try and reclaim their lost home world. The fleet is all but destroyed. However, a lone survivor, Stig Bernard, finds himself on Earth. Gathering a mere handful of resistance fighters, Stig journeys on towards the Inbit's headquarters at Reflex Point in an attempt to gather intelligence and, possibly, discover a way to beat them. (Source: ANN)

At the time of the ceremony of entry to the college, a young boy named Ushino Hayama finds Sara a girl whom he met ten years ago. From this day, a change has taken place in him, and notices that can now control some water. After having succeeded the swimming championships, he discovers deep sea diving.

The third season doesn`t have a particular story behind everything (like "Valkyrie Ghost" in the second season). It just tells 6 stories about the life of Kazuto & Co. with some additions: Raine and Chorus get a house on earth, the last three Valhalla princesses each get an episode, and in the last episode Kazuto and Valkyrie, who in the same episode managed to stay adult, >try< to marry again. (Source: ANN)

Sendo Kazuki, failed the entrance exam for the art college he was applying to, His childhood friend, Kuhonbutsu Taishi forced Kazuki to enter the doujin (private publishing) world.