Izetsuki Orihara is the vampire version of Orihara Izaya and his image was created around Halloween time.
Izetsuki, in terms of personality, is much like Orihara Izaya, but his love for humans is a bit more intense than Izaya's as he can follow someone since the childhood untill the moment of their death and play with that person's life, experimenting as much as possible untill he gets bored or the person dies.
He enjoys eternal life and in no way gets bored with it, feeling indiferent towards his condition as a monster and easly forgeting he is not actually human because for him the actions he takes feel natural.
The only times he actually feels bad for what he is, are when Pritzuo reminds him that he is a monster, which reminds him of the time he became a vampire many centuries ago and the original shock made him refuse to feed untill he could no longer hold it and time made him change to adapt.
Izetsuki's hate for Pritzuo comes from his hability to make Izetsuki dislike his own existence and even knowing it is an irrational feeling, Izetsuki can't avoid it and constantly shows his vampire abilities around Pritzuo just to oppose this feeling.
Izetsuki did not know his mentor, as he was abandoned right after turning into a vampire and never cared to look for him.
(For more information, check Pritzuo's page.)