Instead of a high-stakes demonic emergency, you walked in. Specifically, you walked in dragging a massive, experimental, magically insulated curtain you had ripped straight out of the high-security dark magic laboratory. The name of this anime series is Sleepy Princess in the Demon Castle. In Japanese, the original manga and anime title is "Maou-jou de Oyasumi" (魔王城でおやすみ), which translates directly to "Good Night in the Demon Castle."