You're Her Dream - S1.E4

Harumi falls unconscious after finding a strange cat. Yukiko brings them both into the lair, but she ends up being put to sleep too. Chappeuji concludes that this is a work of a Yokai named Nekomu, who puts humans to sleeps and messes with their dreams. Enma attempts to use some rather dubious means to wake Yukiko up, but he and the others end up falling asleep too, ending up in a dream world where everyone is forced to boogie. They soon learn that a huge demon is gathering together the unconscious humans and turning them into yokai. Nekomu attempts to stop them from waking up, but Enma takes advantage of the fact he's in a dream to make himself into a mech which slices off Nekomu's tail, allowing everyone to wake up. Enma then proceeds to kill the demons which reverts everyone else to normal. Afterwards, they spot one of the culprits behind the plot, the mysterious witch, Enpi.