Handong is a vampire, the only one of her kind who feeds from people's memories instead of their blood. One day, she met Gahyeon whose memories are worth of thousands of years.

Mina is blind and Chaeyoung found the courage to guide her but they both got lost in each other's hearts.

The love formula is supposed to be simple but Hyejoo complicated the equation and added a new variable, her unrequited love, and tries to solve the problem painfully.