The lord's weakness [FREE BOOK] TLW

The fourth princess was supposed to get married to the lord of the world of fire but she was in love with someone else, a simple man from the world of water.

Nobody dares the lord of fire, he is evil, he is a demon shifter and will destroy anything in his path. But the fourth princess chose love over the marriage she never gave her consent to and so on their wedding day, she elopes with her lover but there has to be a bride and so she places her unfortunate servant, Myan in her stead. The lord of fire had no idea he wasn't marrying his beloved princess, what happens when he finds out that she was replaced with a mere servant?