Humanity Has Declined Season 1 Episode 6

The Fairies' Homecoming (2)

As Pion, revealed to be a robot who the heroine now calls P-ko, joins the party, they encounter her companion Oyage, a similar robot who calls himself O-taro, who wants to abandon his mission and live in the strange city. As he sends a killer digger truck after them, they all fall down a hole, winding up at an underground castle. The heroine and assistant are confronted by O-taro, who combines with the slimes to become a 'Killer Death Cat', though the fairies step in to help them. With help from the fairies, P-ko manages to defeat O-taro using a super powered microwave, which in turn restores their memories. After the gang manage to escape the city, it is revealed P-ko and O-taro, whose real names are Pioneer and Voyager, were deep space probes that gained humanoid form. O-taro makes P-ko realise that deep inside, like himself, she doesn't want to leave the warmth of the solar system.