The four main characters are 50-to-70-year-old vampires who have been repeating high school all this time because there's something seriously wrong with them. The school principal allows them to do this because he is also a vampire. Their reasons for repeating high school are as follows:
Because she's been the alpha girl for 35 years straight and she loves being on top and in charge. But not at a business or anything, just at school.
Because her family told her she'd have to begin her royal duties immediately after graduating high school, and she doesn't want to do her royal duties.
Thinks that if she admits to being middle-aged, her body will weaken and she won't be as athletic. But believes that if she stays in high school forever, her body will too.
She wasn't popular during her first attempt at high school, so she's been repeating it trying to get popular while doing nothing differently. She keeps thinking maybe this time, maybe this time I'll be popular. It's been 39 years and she never is.
School principal: Also obviously a vampire, but he claims it's just a costume.
Lance: A boy who hangs out with Azra a lot. Everyone (including him) thinks they're dating, except for Azra. He might look familiar to some of you.
Liam: The only boy Siva has ever liked.
Siva's dad: Siva's dad. A force to be reckoned with.
The vampires' usual activities include turning into bats, bossing people around, human sacrifice, partying, and debating the ethics of trying to date teenage human boys.
In a parallel universe, they are also the Mystikats, of course.