Zenno, a master gamer, has been offered the chance to play the newly-released game, Expers. But when a naked girl appears in his classroom to give him his Expers Suit, complete with real superpowers, he learns that Expers is not just a simple computer game — it is a real-life kill-or-be-killed PvP (Player versus Player) game. Only the main character of the game can survive until the end — but who is the main character? And, perhaps more importantly, who is controlling the game?

Three weeks have gone by since the alien spaceship crash landed on the Graviton City spire, and since then the aliens have been hard at work converting their ship to a pleasure district, hoping to make friends with the humans!… Not. Perpetually late and continually over-eating A-ko, spacy and cheerful C-ko, and brilliant and bold B-ko are about to enter summer break from school, and it just so happens the alien ship is open for business. When a free meal turns into a sob story about how the aliens just want to go home, will it be A-ko or B-ko who can get the ship into orbit again?

It revolves around A-Ko and B-ko's pursuit of a handsome stud named Kay. He likes coke and motorcycles and is quietly courted by both A-ko and B-ko. Meanwhile, C-ko grows very jealous of him... Also meanwhile, the aliens' ship in now floating in the bay and they've tried again to turn it into the ultimate nightspot. Good luck. Catastrophe always occurs when the three 'Ko's get together

A-ko and B-ko are fighting as usual, as C-ko watches from the sidelines feeling neglected by both. Ayumi-sensei has been behaving strangely lately. She's wearing a heart-shaped crystal with a hexagram inside, and is chanting mysterious prayers in private. At the ruins of an ancient civilization, an archaeologist spies a hexagram among the hieroglyphics. Deep in outer space, an alien fleet is on a course for Earth, and its flagship bears the same hexagram shape.