Celebration Night - S1.E44

A young man by the name of Hiyoshi is very interested in searching for ancient evidence to prove that spacemen came to Earth in the past. He goes to look at walls in a near-by cave for ancient scripts to prove his theory, but the villagers think he is crazy. Hundreds of years ago, the Vegans had sent some of their people to Earth. There still is a metal on the wall that they used for landing, and this metal cannot be detected by the radar.