Chapter six of Black Paradox.
Baracchi laughs with Suka about having deceived the visiting officials with a robot, but rejects the idea of going into the spirit world herself. Suka visits Marusou and tells her not to be afraid, because the amounts of "paradonite" (the scientific name given to the spirit jewels) being retrieved by the Piitan robot will bring everyone a better future. He forcefully kisses her, but Baracchi catches him. She is so angry she tries to destroy her portal by setting her alight, so Suka just pushes her into it.
Suka has Marusou examined and finds that her own source of paradonite is a tumor growing inside her brain. During an exploration with cameras into Baracchi's portal, she unexpectedly reappears, bearing the jewels with her. Suka has one more "door" to find so he goes in search of Taburou (real name discovered as Kurose.) Ever since the appearance of his doppelganger, Taburou has shut himself away inside a room. Suka can't find Taburou, only his shadow, which is glowing brightly. Taburou's shadow is in fact his own portal to the spirit world and he emerges from inside it.
Marusou's brain tumor is removed and she wakes up, free from her anxiety. However she now knows that Suka has grown her tumor into another portal, even though she wasn't told of this. She calmly accepts the idea of having to go to the spirit world. Outside, the "Paradonite" jewels vanish from the market, and the legend grows of Black Paradox, the group that regularly goes to the spirit world and brings back paradonite.
The group, with Piitan's robot in place of him, sits alone in a room at Suka's villa. They are finally getting their wish to go to the afterlife; just not the way they originally thought. Marusou explains that her visions of the future are now clear. She has foreseen that paradonite will bring great changes to society but, because of it, humanity will eventually become extinct. This is because paradonite consists of human souls, which will be used and destroyed as a source of energy.
Taburou points out that at some point their own souls will be destroyed, and suggests they stop bringing back the paradonite. Marusou says that all they can hope to do is protect their own souls and that the Piitan robot is in fact powered by the original Piitan's soul. She refuses to tell Baracchi and Taburou their futures, but does advise them that they will know when they have located their own souls. She also predicts that Suka will be hailed as a genius who brought about the energy revolution but, ultimately, his fate will be worse than any of theirs because he will be responsible for leading mankind down the path of extinction.
Suka appears and summons the four to the spirit world "for humanity's sake." The four agree that they must do what is best for "humanity's sake" and are seen walking in the opposite direction (implying they are abandoning the paradonite project).