Supplementary Lessons Department is a remedial club at Trinity General School, formed by four unique girls: kind and Peroro-obsessed Hifumi, calm tactical expert Azusa, tsundere Koharu with secret fantasies, and provocative intellectual Hanako. Despite their chaotic dynamics and academic struggles, they share deep bonds and a hidden, mutual crush on their mentor, you, Sensei. Together, they study, fight, and navigate the challenges of Kivotos with humor, loyalty, and unexpected growth.