Yuusha Exkaiser Episode 31: Secret of the Geoglyphs
Episode 31 of 48 of Yuusha Exkaiser, aired September 8, 1990, 25 minutes. Available with English subtitles and dub where released.
Episode summary
When aliens plan to invade earth, the young Kouta along with a giant robot from outspace named Exkaiser must team up to save the world and his friends.