Sentai Daishikkaku

go go loser ranger - When the Monster Army invaded Earth thirteen years ago, the Divine Dragon Rangers rose up to stop them! With the war raging on, these great heroes are mankind’s last hope!

...or are they?

In truth, the invaders were subjugated within a year, forced to continue to crank out a monster a week for the Rangers to crush in front of their adoring fans! But one monster has had enough. Something has to change! He’ll rebel against the might of the Dragon Rangers and destroy them all...from the inside!

(Source: Kodansha USA)