The Prince sneaks into the castle by disguising himself as a Demon Prince which the demons believing him! He later save a demon slave girl named Prisna who is treated badly by the other demons due to her funny looking horns.
The Prince is reunited with Arietta but she no longer acknowledges that name and calls herself Davre. It turns out Arietta was killed by Tiamat but Tiamat resurrected her using her blood which gave Arietta great powers. Despite this upgrade, she couldn't defeat Tiamat and was repeatedly killed by her. Realizing that humans cannot win against the demons after seeing the demons defeated many human kingdoms, Arietta pledge her loyalty to Tiamat to save the rest of humanity, believing being slaves was much better than the demons killing them. She tries to kill the Prince, believing his presence gives a false hope to the people but is save by Prisna who teleports the Prince before Arietta gives the killing blow.