This the world of Vampire Knight
Cross Academy is different from other schools. It has a Day Class and a Night Class, with different uniforms and no interaction between these two classes. Secretly, students of the Night Class are all vampires, led by Kuran Kaname, a noble vampire who 10 years prior saved Cross Yuki from the attack of a stray vampire. Now a Guardian of the Night Class vampires, Yuki works along with fellow classmate Kiriyuu Zero, a young man with a hatred for vampires deeper than anything she could imagine. Together, they protect Kaname and the Night Class vampires from having their identities revealed, as well as protect Day Class students from any vampire attacks that occur due to a vampire's natural thirst for blood. written by the awesome Hino Matsuri (樋野まつ)
Yuki kurosu (黒主 優姫)
Yuki is the adoptive daughter of the headmaster of Cross Academy. Yuki is a first year student at Cross Academy and is a member of the school's disciplinary committee, which is a Guardian for Cross Academy. In her capacity as a Guardian, she is responsible for the nightly duties of monitoring and protecting the Day Class. Yuki carries the
anti-vampire weapon, Artemis.
Zero Kiryu (錐生 零)
Zero is one of the main characters of Vampire Knight. Zero is Yuki's childhood friend and the only other Cross Academy Guardian. Zero carries an anti-vampire gun named "Bloody Rose" given to him by Kaien Cross.
Kaname Kuran (玖蘭 枢)
is a pureblood vampire, who saved Yuki Cross from an attack by a Level E when she was five years old. Kaname is one of the main male protagonist. Prior to his re-awakening, Kaname was the ancestor of the Kuran family. He is born in the year of the Rooster.
The Night Class is a group of aristocratic Vampires who attend Cross Academy and live on campus in the Moon Dormitory. The students are kept carefully segregated from the Day Class by the Prefects who do their best to keep the Night Class's secret hidden and protect the day class from them. Only a few of the vampires in the night class are given names in the manga/anime and only the small group closest to Kaname is ever really shown, most other members are usually black outlines in the backround, though there appears to be quite a few of them.
Day Class is for the human students who attend Cross Academy, they attend classes during the normal daylight hours. The students live on campus in the Sun Dormitory and are not permitted to leave the grounds after dark.