/pat

Vision of the Past™ shows a little girl being terrorized by a vampire. As the vampire is about to suck her blood, but another (albeit more handsome) vampire kills him, saving the little girl.

Present day, a horde of fangirls gather outside the Night Class's dorm to be… well, fangirls. Yuuki Cross shows up, and tries to shoo them, because it's her duty as a prefect to not let the Day Class meet the Night Class. She fails miserably, as the doors open to reveal… a bunch of bishounen. The Night Class walks pass the cheering fangirls, and Yuuki is greeted by Kaname Kuran. Kaname was the one who saved Yuuki from a vampire when she was small.

Kaname is patting Yuuki when his arm is forcefully grabbed away by the other prefect Zero Kiryuu, also a Day Class student. Zero lectures Yuuki after the Night Students leave, which she doesn't take too well since Zero himself was late. Both Zero and Yuuki are quite aware that the Night Class consists only of vampires.
While the Night Class is in session, Yuuki and Zero meet with Chairman Cross. Cross Academy is one building connected to two different dorms. When the Day Class finishes, they leave and the Night Class uses the same building for class. Yuuki and Zero are assigned as prefects to prevent the Day and Night Class from mixing. Chairman Cross also appears to be the parent of Yuuki and Zero, though foster in both cases. (lol spoiler!)

Yuuki is on patrol when she sees Kaname, and she runs off. Takuma Ichijou cautions Kaname that some of the Night Class vampires only follow him because he is pureblood. Meanwhile, Zero is shown having some… difficulties.

Rau Kuruze?

Caught sleeping in class the next day, Yuuki is assigned supplementary classes along with Zero. Later, Zero asks Yuuki her impression of the Day and Night Class situation. Her positive response is contrasted by his out-for-revenge attitude, as his family was slaughtered by vampires. After Zero leaves, Yuuki spots some Day Class students breaking curfew. Jumping down, she tells them to leave, but senses something and whips out an electric baton. Aido Hanabusa and Kain Akatsuki are there, and Aido says that something smells good. Moving on Yuuki, he says that it came from her, and she realizes she cut her hand while jumping down. Taking her hand, he goes into True Ancestor mode and takes a sip, before bringing her closer to bite her neck.

Aido is stopped by Zero, who holds the former off with a handgun. Zero then fires a warning shot, which brings Kaname to the scene. Kaname promises the deal with Aido and Kain, and Zero drags Yuuki off. He bandages up her hand, then leaves.

Later, Zero barges into Yuuki's bathroom while she's changing, saying that his bathroom is closed. Yuuki wonders aloud if her blood is really that delicious, which startles Zero. He abruptly leaves, obviously distressed. Once outside, he opens his mouth, revealing vampire fangs.

Thoughts:
Rather interesting, the setup of the 'Day Class and 'Night Class'. I would have though that Yuuki would be a vampire, but I guess not. (Well…) I went and read some super spoilers on Wikipedia, and I must say if the anime follows the same path as the manga, I'm definitely hooked.
What I found interesting was that the Day Class wears black, while the Night Class wears white. Is it so that the Day Class is easy to see during the day and Night Class during the night? =p
Vampire Knight's vampires are apparently immune to sunlight, as the Night Class headed to class before sundown. Like in many vampire-related animes, though, a vampire's eyes turn blood-red when in True Ancestor mode.
With regard to Zero, it's unclear whether or not he's a vampire or some freak hybrid, and the mark on his neck is rather curious. His strange behavior around Yuuki is pretty suspect, though.
The artwork is pretty typical of shoujo, with the males all rather handsome and the females with overly large eyes. No complaints here, though. ^^