Yeon Yisol, the top student in her school, suddenly gains the ability to see people's true feelings as hashtags. But when she looks at her first love, Seong Shinu, she sees a tag meant for her: "#The_Trash_Who_Was_My_First_Love"?! The old scars from being abandoned without any explanation resurface. Driven by this, Yisol teams up with Baek Seol, who has her own reasons for hating Shinu. Is it revenge, or are these just lingering feelings? This time... who will be the one to get hurt first?