Makino Tsukushi is the only poor student at Eitoku Gakuen, a school for the rich and privileged. Eitoku Gakuen is ruled by the Flower 4, also known as F4, a group of four boys from extremely powerful families: Domyoji Tsukasa, leader and heir to the Domyoji World Finance Group; Hanazawa Rui, the introverted son of a major corporation; Nishikado Sojiro, a playboy heir to a tea ceremony school; and Mimasaka Akira, a killer with ties to the subway. If a student gets on the wrong side of the F4, they receive a red notice and are bullied and expelled from school. Makino hopes to spend her days quietly, without drawing attention to herself, but one day she stands up to Domyoji in defense of her friend. The next day, Makino receives the dreaded red warning. Even though she is harassed, Makino decides to keep going to school and immediately declares war on the F4, because she is "tough as nails." Her determination catches the attention of her crush, Hanazawa Rui, and, strangely enough, stirs romantic feelings in her worst enemy, Domyoji Tsukasa.