It was only Duke Freed and Koji Kabuto at the beginning.  Hikaru soon joined and piloted the Marine Spazer.  The Drill Spazer was then built, and soon Maria Freed joins the team.

Duke Freed was not one to ask for help from anyone.  He did not want to burden anyone with this responsibility.  Soon, Koji Kabuto explains to Duke Freed that the people of Earth are used to helping each other; Koji emphasized that Duke Freed is now one of them and will need help.

Working as a team was not easy.  Koji Kabuto himself was not used to taking orders from anyone as his history proves.  He was used to doing whatever he wanted whenever he wanted.  Later however, he realized the importance of working as a team.

The Vegan attacks got more and more dangerous, and the importance of the Grendizer Team really showed in the later adventures.  Sometimes, Duke Freed was forced to work on his own if his teammates went down, but he still managed to win many battles by himself.  However, the issue wasn't Duke's ability to win on his own, the issue is teamwork.  Teamwork is so important to win battles quickly and efficiently with the least damage.

The Grendizer Team is not a team to reckon with.  The Vegans found themselves struggling against Grendizer and the new Spazers.  The Vegans even tried to kill Koji Kabuto in their plan to get rid of the pilots.