The Targeted Children! Countdown to Japan's Doom!

The series begins with an episode of Serious Sentai Gachiranger, in which the evil Gedol Empire try to eliminate children from the Saitama District so it will be easier to invade, using a monster named Crabron to turn everyone into a pile of bubbles. The Gachirangers hear about this and set into action, but seem to screw up at every opportunity. The Gachirangers later confront Crabron, culminating in a giant robot vs. monster duel. Upon defeating him, all the children return back to normal. Meanwhile, Hitoha is frustrated that the episode was filled with a lot of stupidity compared to the usual.