The Devil & The Demon (Fantasy/Dark Karma Akabane X OC)

Cora is a unique individual, bullied for being different. Being called names like Shadow, Night Demon, Ghost, etc. Part of it she liked, but other parts she would rather live without. Eventually, her persecutors got to her, leading her to snap, and the mysterious deaths of three students one night.
A detective case was launched, but she had killed without a trace. Still, a group of the top students found out, word spread, and she was transferred to 3-E as a punishment. She didn't feel that she belonged in any other class anyway.
Little did she know of what she really was.
With even adoptive parents beginning to rethink adopting her, and many students wondering why she didn't end up in jail.

Things were going smoothly. That is, until one of her fellow classmates notices her odd behavior, and decides to investigate. Someone who is also different, feared, and teased.
Cora never expected the sly sadistic red head to approach her. Even so, she ends up discovering something greater than everything she's ever experienced.