The drone and fighter ship are Joined Together through their symbiotic relationship that is explained in more detail in the description & "How does your game fit the theme?" prompt, and can be physically Joined Together by docking the drone, or Joined Together by the Nirengeki Double Strike Laser System that fires a massive laser beam between the two.
Perhaps adding a tutorial level would have explained things better, we just couldn't find the time.
I'm glad you liked it! :)