Koshakuka no Akusai wa Keiyaku desu

Jewel, the daughter of a poor deputy lord, enters into a contract marriage with Duke Henry—a man old enough to be her father—to afford the medical treatment for her severely injured younger brother. To teach his estranged son, Blake, a lesson, Henry decides that if Blake proves unfit to be the lord, the inheritance will go to Jewel instead.

Blake happens to be Jewel’s childhood friend and first love, but because of this arrangement, he comes to despise her, believing she is a gold-digging villainess. Years later, after Henry passes away, his will is revealed. It states that for Blake to inherit the estate, he must live as a married couple with Jewel for two years...

So begins a romantic fantasy of a contract couple for a limited time, both unable to be honest about their true feelings.