Isamu Okamoto, an old friend of Joe's and a very skilled student pilot of Professor Tobishima, arrives at the Akane base. After a pleasant evening with the base team, the boy returns to Hokkaido where his base is stationed but his plane is captured by the Gailarians who use him as a guinea pig for an experiment to modify brain cells, in order to enslave the human race. Isamu becomes a slave in the hands of aliens who send him on a mission against a military airport where he makes a real massacre. Since the test was successful, the boy is assigned to another mission and right at the airport where he served, killing his former companions. At the Akanè base, the alarm goes off and Groiser X goes into action, soon clashing with the enemy. Joe and Rita discover that the pilot of the enemy ship is Isamu who does not seem to recognize them. The pilots, distracted by the incident, are captured together with the Groiser who is forced to land.