Yeon Yisol, the number one student in her school, has received the ability to see people's true feelings as hashtags. But her first love, Seong Shinwoo, has tagged her as "#my_first_love_is_trash"! The hurt of being abandoned without knowing why is revived, and Yisol joins forces with Baekseol, who hates Shinwoo. Revenge or regret, who will be hurt first this time?