Nezuko (Demon)

Nezuko Kamado was once a regular human until her and most of her family members were attacked by Mazan, resulting in their deaths and Nezuko turning into a Demon. Nezuko older brother Tanjiro would then travel with her in hopes of finding a way to turn Nezuko back into a human and to avenge their family. After becoming members of the Demon Slayer corps and receiving trainings from the Hashira's, Muzan would make one final strike, leading to an all-out battle between Muzan demons and the Demon Slayer corps. Eventually Mazan and his firces would be defeated, however, in a final attempt to survive, Muzan would attempt to possess Nezuko. Muzan attempt would fail, and his consciousness would fade away, however, this action would make Nezuko Demon side take full control, making her turn on her allies and aligning herself with the demons.