Delly asks Husky if he felt dizzy at any point while in Octopus; he had, and Cooro wonders how she knew. Delly tells Rim and Erica to put the younger children to bed, and come with her. She then asks Husky whether the pearls would sell for a lot, and demands half in exchange for taking him to the one who stole them.
On the way, Delly explains that the thief uses a trick to make people dizzy and steal their wallets. The thief had lived with her gang for a while, but left.
They reach an impassable cave filled with water, the thief lives beyond it. Cooro grows his wings and flies across, and Husky grows his fish tail and swims; the girls are shocked to learn that they are +Anima. Delly turns around to ask Senri whether he is also one, and is surprised to see Sammy there clinging to him.
Cooro reaches the other side and is caught offguard by bats flying around. A girl's voice above him says that Delly and the other girls hate bats because they can move more easily in the darkness. The girl jumps down, revealing herself as a bat +Anima called Nana. They find a rapport in having black wings, but Nana is immediately attacked by Husky who demands his pearls back. Nana notices that Husky is also a +Anima and claims he was tricked by Delly who blames everything on her for being a +Anima, knowing they would find the situation relatable. Husky rushes back, and Cooro follows dragging Nana with him.
Delly orders Sammy to move away from Senri; now that she knows they are +Anima, she regrets helping them. Husky accepts this as proof she was framing Nana. The girls berate Nana without any proof; Cooro comments on them outnumbering Nana, but they just turn their attention on him instead. Sammy points out Nana sneaking away, and they all give chase. Delly reneges their deal on splitting the pearls.
Nana gets some distance, then stops to check that she still has the pearls, which are wrapped around her thigh. She wonders about the other +Anima, but stops when she notices a light moving in the dark. Delly and Rim grab her, pin her down, tickle her to stop her from using her trick on them, and take the pearls. Seeing how many pearls there are, she expects they will be able to rent a house on the surface.
Husky snatches the pearls from Delly; he is frustrated because he had worked hard to earn them. He and Delly squabble over the pearls. Nana uses her ultrasonic screech to stun everyone and then flies away with the pearls. Cooro catches up to her and asks her to return the pearls. Now unable to reach them, Delly shouts that she hates +Anima. Nana has a flashback of being chased through some woods, and drops the pearls which Husky and Delly both grab hold of. Nana cries that she never wanted to become a +Anima. Husky and Delly both cover their ears expecting another ultrasonic screech, but end up they end up snapping the string threading the pearls, which all fall down into the dark depths.
Later, Cooro, Husky and Senri leave Octopus. Cooro comments on how unlucky Husky is. Nana watches them leave from a distance. Delly approaches her and apologizes. She explains that she was jealous of Nana, and felt mocked when Nana left. Nana had known the others disliked her and had chosen to leave because of it. Delly tells Nana to go with the other +Anima.