Tsukuyomi: Moon Phase is a 25 episode series, with a 26th bonus episode (unrelated to the main story). FUNimation released the series as Moon Phase.
Moon Phase is a vampire anime. But instead of being totally bad ass like Hellsing, or sexy and Gothic like Vampire Knight, it's sickeningly cute (or it tries to be) but also too serious for its own good. I would have enjoyed it far better without the young vampire Hazuki/Luna, but then there wouldn't really be a story. Actually, I think there would, because the other characters are really interesting, there just wouldn't be a focus or a catalyst.
My problem with the show lies in its failed effort to balance overly cute characters with a serious story line. Ditch the idiotic and pointless random cat ears (and sometimes tails), have Hazuki look older than a 12-year-old (and act older than a 5-year-old), and it might actually be a decent show. The darker sides of the story (particulary Elfriede's past, Kouhei's latent powers, the disappearance of Kouhei's mother which I don't recall ever having been fully explained, or the also rather unexplained death of Hazuki's mother) would make a great show on their own, but they're over shadowed by too many goofy and over dramatic scenes.
Moon Phase follows freelance paranormal photographer Kouhei, who appears to be in his early 20s, and is a magnet for paranormal activity, even though he can't interact with it in any way himself. He can't even see the spirits that tend to congregate around him. He is also what is called the Vampire's Lover, which means he can't become a vampire's slave, and his blood has the power to free other vampires from their masters. While on a photo shoot of an old German castle he runs into Hazuki (also known as Luna, her more malignant alter ego), a teenage vampire who is being held captive in the castle. By drinking Kouhei's blood she frees herself and is able to escape the castle. As she is basically just a child, Kouhei takes her to his home to live with him and his grandfather Ryuuhei who owns an antique shop, and who is also a powerful spiritualist and exorcist. Many vampires are out to get Hazuki both for her power, and to bring her back under control at the castle. Kouhei and his family (which includes his grandfather, his cousin Seiji, his fiancee (by an arranged marriage) Kaoru, Kaoru's twin sister Hikaru (engaged to Seiji), and Yayoi, a power exorcist in the family) work to protect Hazuki from those who are out to get her. Along the way the vampire Elfriede, who once worked to capture Hazuki, switches sides and also helps to protect her.
I'm a bit bothered by how actively Kaoru and Hikaru, who look to be about 12-years-old, pursue their affections for the much older Seiji and Kouhei (particularly by Kaoru's persistent attempts to pull Kouhei's attention away from Hazuki by acting like a cat). On top of the obvious romantic sensibilities between 14-year-old Hazuki and Kouhei. I know that these sorts of relationships aren't as big of a deal in Japan as they are here, but it doesn't make me any less disturbed by them. Though I don't suppose a brother-sister relationship is really appropriate when the girl in question is "kissing" you once a month so she can suck your blood. I was also kind of annoyed by how often the story needlessly draws out certain plot twists or secrets, especially when they're so painfully obvious to the audience. Hiding it from the characters is one thing, but continuing to try and make it some absurd mystery to the audience when they already know the answer is unnecessary.
The animation is quite good, at least. Though it's got to have one of the most annoying opening songs I've ever heard. I also must mention again how much the cat ears that appear on the heads of various characters (mostly Hazuki) for no real reason (other than to look cute, I assume), and on random pieces of scenery, really annoyed me. Moon Phase isn't horrible, though it could be much better. Maybe the balance is better in the manga, but I doubt it. I wouldn't watch it in English though. Hazuki's English voice is probably one of the reasons I disliked her so much, and the same goes for Kaoru. I also wondered why "cute animal-like side kick" equals "speech impediment." I watched it on the FUNimation channel, so I didn't have the option to listen to it in Japanese. Unless annoyingly cute vampire lolita girls are your thing though, I wouldn't really bother.