Cradle of Heaven

Three years ago, the celestial empire came under attack by the demons. With his kind on the verge of extinction, the celestial being and emperor, Kasin, is tasked to go down to the human world and find a way to restore peace. After three years without much progress, he encounters Daran, a merchant who has disguised herself as a man to travel and sell medicinal herbs. Daran was born with the power to heal anyone with a single touch. This ability makes her the exact person Kasin needs on his quest. Although Kasin swears he has no interest in men and is only keeping Daran with him as an aide, the more time passes, the more he finds himself becoming attracted to the special merchant…

Where two individuals formed a contract together because they found out that they needed each other and swore to protect one another. At first, it was just a simple and ordinary contractual relationship, but it seems like they're beginning to pay attention to each other.