Seoli (서리)

When others were reincarnating as beautiful people or adorable animals, I ended up in the body of a creepy monster living in the male lead’s closet. Why? Not only that, but I also became the nasty monster that torments the male lead. According to the original story, the male lead was supposed to fear me. But— “Your horns are more beautiful than roses.” “Can I give you a name?” The male lead doesn’t seem to be scared of me at all. I thought it was fortunate that I, now a tenant (?), was able to get along with the male lead, the owner of the room. “I’m scared to sleep alone. Let’s sleep together.” But I didn’t expect us to get this close…. Dedrick stared at the monster sleeping soundly in his closet. This monster, who had suddenly appeared one day, had saved him from his hellish life. The corners of his lips curled up in satisfaction. ‘My very own monster.’ Something that was only his, something he would never let go of.

By imperial decree, Duke Tristan receives his bride from the Kingdom of Haniel to form a marriage alliance between the two nations. After they consummate the marriage, his bride reveals that she's just a maid sent to test if he can do his business in bed...