It's not so much a plot as a backstory, but what I have planned is this:
Long ago, there was a beautiful doll who sat locked away in a china cabinet. Unlike most dolls, a spirit had taken residence within her small porceline being, eventually forming into a soul. Most dolls don't have souls, let alone sentience, so this was bound to attract the attention of magical creatures and magic users alike. Her owner, a powerful wizard, was a lonely man who wished for a beautiful bride with a heart as pure as snow. So, obviously, he turned the doll into a human. WHOOOPSIE DAISY s**t DON'T WORK THAT WAY. She bolted almost immediately, wishing to be free of her ex-owner so that she may see the world beyond her wretched prison. As she became quite the lively maiden, learning to salsa dance and party with the wildest of nobles. (She also learned that she had a huge fettish for the crazies.) She unintentionally caused trouble wherever she went, both from breaking the heart of the man who turned her human and her greed and desire for the finest of clothes and jewels. The story will start as she's confessed to by the latest crazy/yandere to come along and have his heart stolen, and obviously, she accepts. From there on she hides the fact that she used to be a doll and manipulates her new lover to the best of her ability whilst he...does whatever the player wants him to, so long as he remains a yandere and not human, vampire, or a typical demon. (Otherwise, species entirely up to the player) (I know, I know. Lazy of me. But I like to leave as much room for interpretation for the other player as possible, as too many restrictions and totally ruin the fun of the piece.)