Returning home for summer break, Sol encounters a mysterious man named Romi, who appears to be her mother’s boyfriend. As an uncomfortable cohabitation begins, Sol becomes entangled in constant suspicion and misunderstandings. But as Romi’s sincerity slowly reveals itself—alongside conflicts with her mother and the feelings of her childhood friend Dohyun—Sol grows increasingly confused. In the heat of summer, fluttering emotions and misunderstandings intertwine in a story of youthful tension and romance.