To save his Kingdom, the King of Seoul seeks out the help of the powerful Mother of Spirits. Beside the fact that she promises him future prosperity for the people of Seoul and the Royal family, she also makes it clear that this is subject to the arrogant Crown Prince Lee Taemin to marry the humble commoner Son Naeun.  

After taking over his father’s insurance business and agreeing to an arranged marriage with the daughter of the rival company to form an alliance, Taemin is yet expected to fulfil one more duty - to bring a child of his own into the world and secure the future of the business. However, since his wife Naeun is unable to produce an heir, the couple is asked to go through a surrogate by their families so that the successor at least remains within the same bloodline.