Synopsis: One Day, Suddenly, Seoul Is

A catastrophic outbreak of the variation virus devastated Seoul, catching a school trip in its chaos. Yeon-u had been hoping the trip would create an opportunity to get closer to Soyon, whom he had secretly adored for a long time. However, their excursion into the city took a frightening turn when an unknown pathogen targeted Yeonwoo-ne Class. The contagion triggered a transformation in the infected individuals, turning them into terrifying monsters and plunging the school trip into a nightmare. Can Yeon-u and his classmates survive the outbreak without harm?