An Oath in Space
Dr. Umon calls Daisuke and Koji to show them the way that Grendizer and Double Spazer can unite together and fly. The objective of this is to minimize the need for Grendizer to have to lock in and out of Spazer as these are Grendizer's weakest moments and he is helpless in them.
Aired 06/06/1976EP 36 - An Oath in Space
1975
UFO Robo Grendizer
Duke Fleed is a survivor of the Fleed Planet who is escaped to the Earth, onboard a mysterious "spaceship", where is raised by Dr. Umon as his adoptive son, and known as Daisuke Umon. Years after his arrival, he's faced with the threat of King Vega and his army, who want to conquer the Earth. With his friends Koji and Hikaru (and later his younger sister Maria Grace), Duke decides to fight back using his best weapon - the almighty Grendizer.