Yuusha Exkaiser Episode 37: Monster Library
Episode 37 of 48 of Yuusha Exkaiser, aired November 3, 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.