A giant robot powered by gravity sounds cool until you realize the show is actually about a rich man's vanity project defended by whatever misfits wandered onto his private island. The premise is absurd on purpose, and it commits to that absurdity with zero apology. You're watching a 2002 mecha comedy that knows exactly how ridiculous it is, refuses to explain itself, and somehow makes that refusal the whole appeal.

In 2041, a new enemy called Zeravire suddenly appears in the solar system and begins wiping out every military installation in its path. Wealthy Klein Sandman already knew this invasion was coming and has quietly been building an army to meet it. His ace is Gravion, a giant robot that draws its energy from gravity. When young Eiji slips into Sandman's base searching for his missing sister, he meets another young man named Toga. The two end up fighting side by side with four others aboard Gravion to hold off the Zeravire. The series mixes giant robot science fiction and adventure with a comedic streak across a short thirteen-episode run.