Yuko is a villain. She's got horns, a tail and the ability to enter your dreams. (Technically she's a succubus, although she doesn't seem to know what that means and there will be fireworks when she eventually finds out. The series has no intention of going there.)
Momo is a magical girl. She has a pink outfit, magic and super-strength. She's already saved the world or the city at least once.
Yuko's goal is to drain Momo's blood and offer it to her ancestor (a little talking statue that the family uses as a doorstop). They're mortal enemies. Yuko's always working on her devotion to the cause of evil, with dialogue like this: "Embrace your weakness, give in to utter depravity and stray from the path of light." However she's also a good-natured, slightly dim schoolgirl who's terribly fond of Momo and will look after her when she catches a cold. They swap phone numbers, so that they won't keep each other waiting for their fights to the death. (Yuko couldn't win a fight with a kitten, so magical girls all think she's adorable and will coddle her at every opportunity. Momo seems to like having a best friend who keeps promising to murder her and drain her blood.)
They buy presents for each other. If one of them's in trouble, the other might become her subordinate. In fact, Momo's arguably more evil than Yuko. Admittedly she's not the one who keeps delivering villainous catchphrases (which never stop being funny, incidentally), but she's better than Yuko at thinking up plans for evil and ways for abusing your superpowers.
This is a lot of fun. I enjoyed it a lot and I hope they make another season. Admittedly I'd have been happier had Yuko's evil drift been in the opposite direction, but we all know she'll never turn officially to good. Yuko trying to be evil is the show's central joke.
1. The cute, twinkly music for Yuko's demon girl transformation sequence. It's so inappropriately adorable. (The outfit is effectively an Evil Magical Girl costume, except that it provides only a negligible power-up. Yuko dislikes how revealing it is.)
2. Yuko's little sister, Ryo, who's diligent, serious and wants to support her beloved sister's efforts to conquer the world. Even magical girls love Ryo and can't help wanting to encourage her in this.
3. Momo's darkness. This isn't just a fun comedy. Momo never smiles, has a scary hidden vulnerability and doesn't have good memories of being a magical girl. She's far better than Yuko at almost everything, but she's also fairly gloomy and unhappy, while the irrepressible Yuko has friends and a loving family. (Momo's also filthy rich, thanks to her world-saving activities. Yuko's family, on the other hand, is literally cursed with poverty.)
4. The school. A common trope in magical girl shows is that the heroine has to keep her powers secret and can't tell anyone, even her family. Here, on the other hand, everyone thinks Yuko's horns are cool and will cheerfully mention that there's a magical girl in Class A.
YUKO: "I grew horns and have to find and murderize a magical girl to undo the family seal. Isn't everyone too calm about what I'm saying?"
FRIEND: "This town's full of weirdos."
This show is charming and funny. Yuko's Crisis Management form is a bit sexy, but the art style's basically fun and fluffy. I want more of this show, because I want to see Momo and Yuko's relationship developing further. I'm a little disappointed that the source material is only a four-panel manga, but I might go looking for it anyway next time I'm in Japan. (A four-panel manga can still have story and character development. It doesn't have to be a gag comedy, although I can see this material working like gangbusters in that format.) In its ostensibly evil way, this show's really rather nice.