Appearance: 5'5" and all of it in your face

Name: Haruko Mori

Age: 17

Gender: Female

Personality: Cheerful and full of energy even first thing in the morning, Haruko is best known for being a bit of an airhead - her grades are barely passing and she never seems to focus in class. She prefers instead to talk with as many people as possible, even total strangers, though this has earned her plenty of friends both within and without the school. The only school-related thing she really does well in is sports clubs - she has a fondness for tennis and judo. She is also somewhat talented in getting favors out of people, typically to make another person happy or to avoid doing a task she deems impossible. Sure, she's not book-smart and can be easily confused, nor does she normally keep up with the news on her own, but she does have a fair bit of common sense. She's a good listener, even if she's not very good at advice or at keeping a secret. Above all, she wants people around her to be as happy as she typically is, and gets genuinely upset if she ends up running herself ragged for nothing. Haruko tries to live life without regrets, though she hasn't entirely succeeded.

Villain Appearance: When night falls...

Villain name: Plague

Powers: Transforming into Plague gives her a few benefits - she will not keep any of her wounds gained while transformed, she feels fully rested afterwards, and is not bound by her health. Plague itself has its own powers - it can spread sickness through inflicting a wound, fly, turn intangible, and fire arrow-like feathers from its wings. However, to sustain its powers in full, Plague must consume human flesh, healthy or diseased, and must shun bright light.

Transforming item: At will, to a degree - if she is feeling ill or generally unwell, Plague can easily slip out. If she is feeling well, Plague is nowhere to be found. In addition, it must be at night.

History: Haruko is the child of divorce - both she and her sister were split at age 8, though not before there was a physical altercation. For over a year, Haruko seemed reluctant to believe that the divorce was final, frequently asking her mother when her father was coming home, even when she began dating other men. It took Haruko a few years to accept that her father wasn't coming back, and a few more months to warm up to her mother's current partner. When he offered to teach her judo, that got her on his side.
Beyond the unfortunate split, though, Haruko lived a fairly charmed life. She tended to attract people to her naturally and, even as a child, made many friends. Her parties were enormous affairs, usually held out of the house. Some people kept in touch as schools and clubs changed, some moved on without her, and a few who were significantly older were pulled away from her by work and family moving. None of this dissuaded her at all, as she knew there were always more people to meet. Besides, as far as she was decided, it didn't make a person any less of a friend just because they weren't known for long.
After one of her parties, over the summer break, she was cleaning up when she found a peculiar ring with a skull on it. As she was the only one left, she decided to hold onto it until she could find its owner. If she didn't, well, it was oddly alluring in its own morbid way, and no one would mind if she kept it, right?

Other: Haruko doesn't speak much of the divorce. She knows where her father moved to but is reluctant to have a reunion.

Plague seems to have a personality separate from its host - it puts its own health and survival above everything else, thus why it has no hesitation feeding on people. While it can make do with, say, a limb, it likes eating as much as possible and seems to be genuinely concerned about starving. Plague is highly aggressive - if it moves and is human-shaped, it's probably a meal, and if it pulls Plague off a meal, it must be destroyed. It's also not terribly smart, though it is capable of basic hunting strategies. Pretty much, it's a big ferocious animal barely kept on any sort of leash and if it wasn't for the fact it has some speech - mostly learned from its victims, resulting in generally nonsensical phrases and horrific screams - it'd probably be considered nonsapient.