Usui Kenta's mother. She is often depressed since she has trouble holding a job. In each job she has, many men will fall in love with her. When she refuses them they start to harass her which leads to her getting fired. 

(Source: Wikipedia)

Maaka Karin comes from a family of vampires living in Japan, but she is not a normal vampire. Vampires are normally supposed to drink the blood of their victims but Karin suffers from a condition that causes her body to produce excessive amounts of blood. About once a month, she has to get rid of the excess blood by giving it to her "victims." But she somehow manages to go to school like everyone else her age. 
Well, things are about to get more complicated. When a new student, Usui Kenta transfers into Karin's class, she starts producing unusually huge amounts of blood, almost as if in reaction to him. Worse, he happens upon Karin's true nature...

Karin is a cute little girl who also happens to be a vampire...with a twist. Once a month, she experiences intense bleeding from her nose--we're talking gushers! In other words, she's a vamp with blood to spare, so rather than stealing blood from humans she actually gives her blood to them. If done right, this can be an extremely positive experience that benefits the "victim" as much as the vampire. The problem is that Karin never seems to do things right!
 
(Source: Tokyopop)
 
Note: Includes 5 extra chapters.

Fumio Usui