Kazuki Yotsuga seems like your typical average boy, but what's unique is that he has brief glimpses of a parallel world only he can see. It doesn't take long until the popular Mitsuki Sanada takes notice of him, stating she is "interested" in his visions, which Kazuki has written on his Internet blog. Mitsuki takes him to her father, Ken Sanada. The mad scientist claims he has bridged the gap between the real and parallel world; he enlists (or rather forces) Kazuki as a test subject to prove that theory. The experiment is successful; Kazuki finds himself in the parallel world and witnesses a battle between two giant robots. Hartzenen, the white robot Kazuki previously named, falls in battle. As he sees the pilot injured while trying to escape, Kazuki comes to her rescue and somehow activates Hartzenen. Despite his reluctance, Kazuki manages to control the robot and disposes of the enemy robot in front of him.