A musai is a creature who secretes a toxin on her lips. This toxin, when applied to skin (or in this case bone) promotes a crazed obsession over the musai. (Y/n) is a musai, running from town to town with her mother as they are persued by helous past lovers. The bad sanses, however, kidnap poor (y/n) to work for them. And the more time she spends with them, the more she changes... The concept of the musai is from Grimm, a tv show. I recomend it. Also, musai and other wesen can only be seen when they want to be seen, so until (y/n) woges, she will look like a human.