Kabayama Atsushi was a child prodigy, but now he's 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 world-by sleeping with Trance's "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 world's fate really depend upon Atsushi having sex with Tsubasa?