Yumekui Merry is a solid series that could have been better if it had more episodes to work with.
Its 13-episode length doesn’t give it enough time to develop the central plot and the end feels more similar to the completion of an arc rather than that of a series. They still haven’t found a way to send Merry back to the Dream World and the main villain hasn’t even made an actual appearance yet. This leads me to believe they are planning on having a second season, or so I hope.
Yumekui Merry had a strong start involving the intriguing set of worlds: Reality, the Dream World, and a place in between those two. Yet the series spiraled downwards with somewhat episodic battles against dream demons, but regained its focus in the ending mini-arc involving Isana. I would have liked if John Doe didn’t vanish from the second half of the series since he was one of the more interesting characters. However, Engi and Kounagi made up for that.
Other than that, the OP sequence was the best part of every episode. It complements the song, Daydream Syndrome, quite well. Now I’ll end with a quote of the revelation that Yumeji finally remembered in the final episode:
Strength in a Dream…is the strength of will!
And this is something John Doe told him in episode 6, sigh.