Synopsis
Summer, 2000. Eleven-year-old Yusuke and his classmates are camping in a woods when suddenly they see a bright light streak over the treetops and into the woods. The boys take off into the woods towards the light. There in the ground, growing, they find a small round metallic object. Just as Yusuke reaches to touch it, the mysterious object pops up a set of eyes and the object says;
"I am Tetra, I meet Yusuke".
Startled Yusuke replies "Your name is Tetra? Cool!"
Tetra is kept from adult eyes in Yusuke's closet. Tetra creates wonderful gadgets using "never-seen-before" technology. It would appear Tetra was designed with artificial intelligence. But where did Tetra come from and what is its purpose? As the relationship grows between Yusuke and Tetra, these questions are answered. Yusuke and his friends, along with the genius physicist Kanzaki, who studies time machines, investigate Tetra's secrets.
Meanwhile, 100,000 kilometers above Earth, a massive fleet of mysterious alien spaceships belonging to the Voidians is anchored, targeting Earth's oceans. With Earth's crisis rapidly approaching, Yusuke, with all his courage, boards the Gungelion, a combat robot created by Tetra, to protect Earth and Misaki, who has been abducted by the Voidians. Will they be able to save Earth? And what will become of Misaki's life?
