A pitiless demon becomes powerless after getting entangled with an icy heiress, who may hold the key to his lost abilities — and his heart.

The series is about an incident that takes place when the owners of the boarding house called 'Guest Summer Palace', which breaks stereotypes, and boarders with secrets gather to find Lee Seol who disappeared 13 years ago.

Shin Sol-i isn't shy about her unrequited crush on Cha Heon, her next-door neighbor. One day, she gets an idea to write him the perfect love letter.