The substitute bride is captured by the yandere lord

Lala, the daughter of a nobleman, is sent to the castle of Walter the Feudal Lord, in place of her sister who has eloped. Lala is prepared to be treated harshly, but for some reason, Walter grows fiercely attached to Lala as though he was never even remotely engaged to her sister to begin with. ...... It's a story about a love fantasy of a yandere in a fantasy world!