She's the previous demon lord but she chooses to use a spell that can reincarnate herself as a human so she can build a better relationship between monsters and humans, she's alive and well as a human.
@BloodKing1 ahh that one, yeah kind of similar but played differently since she's not the main character here. She more of a supporting cast dragged around by Haruto and Charlotte, and her subplot is not that important to the main story.