Kaibutsu Oujo: Konsui Oujo

昏睡王女

Episode 26 included in the ninth DVD volume of Kaibutsu Oujo.

Flandre has gone missing within the mansion and Reiri, Riza, Hiro, and Hime have been left without any of their powers. They quickly deduce they’re in a nightmare after exposing an illusion by setting a curtain ablaze. They have to work to find their way out of the nightmare while facing tough opponents.

(Source: Wikipedia, edited)