After brutally beheading the monster that murdered his parents, a boy named Ise is shunned by his village as a monster. With no remaining desire to live, he declares that his revenge will only truly end when every last monster is completely eradicated.

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.

Olin, a modest and intelligent marquis's daughter, is blindsided when an arrogant noble publicly announces that he is breaking off their engagement. Calmly, she informs him that they were never engaged in the first place—her actual fiancé is an entirely different man: the handsome Duke Lyute. As the misunderstanding unravels, Olin's carefully concealed talents and true status come to light, leading to a satisfying comeuppance for those who underestimated her and a heartwarming romance with the man who has loved her all along.