Imanishi Uta and Kujo Misono are cousins ​​who have been raised together since childhood. Uta is a hard worker who aims to become a freelance writer while working part-time at an izakaya, but she is stubborn and not good at expressing her emotions honestly. On the other hand, Misono is a cute and spoiled character who is loved by everyone. These two contrasting people live together in an apartment in Tokyo, are family members, and are like best friends. However, in fact, Misono has a devilish cold-hearted heart...! Uta, who lives together without knowing that Misono has a hidden side, is gradually driven to ruin. When Uta eventually realizes Misono's betrayal, she despairs and vows revenge to counterattack, but... Adapted from the novel "Akuma wa Soko ni Iru" (悪魔はそこに居る) by Shimizu Seika (清水セイカ).