Sungjin High School is thrust into chaos as an alien invasion begins, unleashing violent insect-like creatures worldwide. With the South Korean military overwhelmed, mandatory conscription is imposed on all third-year high schoolers, forcing them to undergo military training while facing impending university exams. Platoon leader Lee Chun Ho guides them through rifle shooting, combat, and obstacle courses, all in their school uniforms. Class teacher Park Eun Young strives to protect her students. Can these high schoolers become saviors in the face of global doom? (Source: MyDramaList) ~~ Adapted from the webtoon "Duty After School" (방과 후 전쟁활동) by Ha Il Kwon (하일권).