Kabayama Atsushi was a child prodigy, but now hes just a regular high school boy. One day, a mysterious man from another world named Trance appears before Atsuhi and asks for his cooperation. Apparently Atsuhi is the chosen person who can save the worldby sleeping with Trances sister, Tsubasa! Already confused and overwhelmed, Atsushi is also targeted by a woman with strange powers that seems to know Trance and is determined to kill Atsushi. Does the worlds fate really depend upon Atsushi having sex with Tsubasa?