Kouhei Morioka, Black Sheep of a family of powerful psychics and spiritualists, has less spiritual energy than the average Muggle. In his job as photographer for an occult magazine he encounters Hazuki, a young girl trapped in a castle by a magical barrier (Kouhei is so lacking in spiritual energy that the barrier didn't notice him). After he promises to help her out of her confinement, she insists on giving him a "kiss," then bites him on the neck.Now, usually in this story when a vampire bites a human, the victim loses all free will and becomes the vampire's slave. This doesn't happen with Kouhei (spiritually retarded, remember?). This doesn't keep Hazuki from acting like it did and throwing a temper tantrum when he doesn't humor her.Anyway, Kouhei smashes the crystal making the barrier, gets Hazuki out, and she spends the rest of the series living with Kouhei and his grandfather in the grandfather's shop, and fighting off attempts to bring her back to her prison by other vampires.
Accidental Kiss: Episode 21, which has Hazuki and Hikaru end up kissing each other after a villain throws the latter onto the former.
Accidental Pervert: Episode 25. Kouhei was just using the bathroom. How was he supposed to know Hazuki was taking a shower?
Adorable Abomination: Once Kouhei gains the ability to truly perceive spirits, he sees Hazuki's true form (which was apparently hidden from everybody) and freaks out at her.
Anti-Magic: Kouhei, who can't cast magic but is also impervious to it.
Black Blood: Red blood is okay for vampire bites, but blood from very serious wounds (like, say, a hole dug in someone's chest) is black.
Badass Normal: Kouhei, who valiantly fights for his friends despite lacking the spiritual powers the of his family possess. He eventually becomes more powerful after training himself in order to better protect his loved ones.
Bubblegum Popping: Artemis is almost always chewing gum, but the only time you know is when she blows a huge bubble.
Cat Girl: Parodied. Hazuki is always wearing cat ears and it's a motif to see cat ears or cat ear-shaped things throughout the series. The cat spirit, Heigi, is an actual cat girl, however.
Chick Magnet: Kouhei tends to attract all the powerful female characters in the series.
Costume Porn: Courtesy of the family, Hazuki wears several different outfits throughout the series.
Cultural Translation: The English dub replaced the closing trailers' horrid Japanese riddles with horrid English riddles. Apparently there's a law of Conservation of Corny involved in the translation process.
Daywalking Vampire: One of the vampires Kouhei meets has this ability, namely Hazuki, though they only find out later on, after Elfriede temporarily gains the power through Hazuki's blood.
Dirty Old Man: Kouhei's grandfather has minor shades of this, as he's the one that initially bought Hazuki her outfits and seemed really keen on the suggestion that Elfriede suck his blood and make him her slave.
Dojikko: Kaoru. Her gigantic glasses don't do much good, it seems.
Drop the Washtub: Done liberally throughout the whole series. Various characters will get bonked on the head numerous times by one whenever they do something remotely stupid. It's all for the Rule of Funny, and at one point one character actually realizes exactly what he's saying, and catches the tub.
Taken absolutely Up to Eleven when the entire HOUSE of the cast gets bonked by a giant washtub.
False Camera Effects: Strange things happen all the time, but one of the best examples has nothing to do with the camera itself. Instead it happens when a microphone hangs in the view as if the audio assistant had a weak arm and no one noticed during editing. Also a spotlight is standing around for no reason at all.
Fanservice: There are random bits in the anime that consist of nothing but one of the characters (usually Hazuki) posing (sometimes suggestively) in various outfits (sometimes fanservicey). There's also the fact that most of the female cast members (particularly, the ones interested in Kouhei) consist of young and young-looking girls.
Faux Paw: Hazuki does this especially in the opener.
Fight Unscene: Several of the fights in the anime, rather annoyingly, cut away from the action to show a piece of landscape or architecture while you can hear the fight going on. A lot of this issue was fixed for the DVD release, leading to some confusion between groups of fans who have only seen one version.
May/Mayfly-December Romance: All the relationships portrayed, projected, implied, or otherwise, involve people who are with people don't look anywhere near the age of their partner. The biggest examples being Kouhei with Hazuki, and Grandpa with Elfriede.
Mega Manning: Vampires each have a unique ability that other vampires can borrow with a sip of blood, or steal permanently with a fatal drain. Hazuki's copyable ability is not dying when exposed to sunlight, hence her importance in the eyes of other vampires.
Moon Rabbit: The opening makes a bit more sense if you know about the Rabbit on the Moon and its mortar.
Mundane Utility: Hazuki has the ability to completely eliminate her life signs and sit completely still for hours. She uses this catch thieving birds, and to allow Kouhei to take an amazing long-exposure photograph of her.
Scary Shiny Glasses: Most frequently Elfriede, but Seiji and even cute little miko Kaoru flash them on occasion. Also notably, Seiji has one short scene where only one of his lenses is shiny and it's not played for sinisterness.
Something Completely Different - The last episode takes place in the middle of the ocean for no good reason. One of the characters is driven insane by how little sense this makes.
Tsundere: Hazuki is a classic Type A towards Kouhei.
Weirdness Censor: Episode 26 exaggerates this beyond measure. To explain, the house the cast lives in is floating in the middle of the ocean, and apart from Seiji absolutely no one finds this particularly strange. They even laugh at him for trying to convince them that this situation is bad.