Himagus

A planet called "Himagus", had been planning to take over Earth and terminate mankind for decades. And when that did happen it was all because of two Himagusians, one a werewolf and the other a magus, who had lived on Earth for seven years to complete this task. But as they both fell for one human girl, they kept her alive.

And now it's up to her, to attempt bringing humans back, take her revenge on these Himagusians or admit she's in love and live happily ever after.