Now for the plot, Tube's latest plan involves turning humans into protists, so that they can have more monsters in their arsenal. They experimented the boy who accidentally discovered this plan; he did end up transforming into a monster but is lucky enough to maintain his humanity. This is when the episode starts to become really interesting. He tries to communicate with humans, only to be attacked by them out of fear. To make matters worse, he can't speak the normal human language that he resorts to pointing things if he wants to say something.
Finally, how the girl accepted what happened to the boy. It's really touching scene; at first we see her fear on the boy's current appearance until she realized that it is her friend. Because of this confirmation, our heroes learned Tube's plan and is able to stop it. As for how they were able to transform the boy back to normal, the method on how they did it is quite expected. As for the rest of the episode after this, it's your typical Super Sentai fight scene and ends with a giant battle featuring Great Five.