Yuki is the adopted daughter of the Headmaster of Cross Academy, Kaien Cross, and has grown up and become a prefect for the school with one main purpose: for vampires to coexist peacefully with humans
Through a cruel twist of fate, Zero becomes a vampire himself, having been bitten by pure-blood vampire, Shizuka Hio, four years before.
Now Yuki must help him fight his curse, as well as recover the lost memories of her past.
She must also discover why Kaname, who leads the group of Night class (all of which are also vampires) at Cross Academy as their President, saved her that night and what deep dark secret he is keeping from her.
Yuki Cross is the adoptive daughter of the headmaster of Cross Academy, and a Guardian, one of the members of the school’s disciplinary committee.
Ten years prior to the start of the series, Yuki was rescued from a vampire attack by another vampire, Kaname. She lost all memory of her life from before the attack, and was adopted by Headmaster Cross.
After Zero’s vampire nature is revealed, she begins giving him her blood to drink. However, Yuki loves Kaname, who has always been protecting her and has been by her side during her childhood as a vampire.
When Rido Kuran, their uncle, resurfaces at Cross Academy, Yuki’s memories are unlocked, revealing that she is actually a pureblood vampire, both Kaname’s sister and his fiancee.
Zero Kiryu who is a year older than Yuki Cross, comes from a vampire hunter family. His parents were killed by the pureblood vampire Shizuka Hio after they were ordered to assassinate her lover, a former human that had not yet fallen to level E. Zero was taken in by the headmaster of Cross Academy and became a Prefect (Guardian), alongside Yuki Cross.
He has a great hatred for vampires because of what happened to his parents, but it is later revealed that he himself is a vampire as a result of Shizuka’s attack.
It is also later revealed that his twin brother, Ichiru, also survived the attack and lived at Shizuka’s side.
After he consumes Shizuka, Kaname lets Zero drink some of his blood to keep Zero from losing control of himself in order to protect Yuki.
Kaname Kuran a pureblood vampire, saved Yuki from an attack by another vampire when she was little. He is the class president of the Night Class, much feared and respected by the other Night Class students.
While he is cold and authoritative towards his fellows in the Night Class, he is always kind and sweet to Yuki. He has shown that he cares deeply for Yuki, and loves her in a romantic sense. He allows Zero to live because he knows his death would sadden Yuki, and because Zero is useful. He is both jealous and angry of Zero for biting Yuki and endangering her life.
Kaname has been raised as Yuki’s older brother. At a young age they had pledged to marry each other when they grow up, just like Haruka and Juuri, who were siblings yet married to each other. It is common for pureblood siblings to marry as it is essential to keep the bloodline pure.
Also, a fact yet to be revealed to Yuki is that Kaname is not her “true brother”. He is actually the ancient ancestor of the Kurans, and Rido is his master who awakened him from his grave, making him unable to kill his ‘master’.