Three Otaku girls attending a girls' high school in Kyoto, known as a bottom-tier school, have been treated as the lowest in the School Caste within the school. One day, a breathtakingly beautiful girl named Hotaru transferred from Tokyo. While the three were gathered in the "Otaku Club"—a biology club in name only—immersed in their respective hobbies, Hotaru appeared wanting to join and confessed, "I'm an Otaku too, you know." The four gradually deepened their bond as friends, but one day, Hotaru jumped onto the tracks and died. Without knowing the truth, years eventually passed, and they began to be ensnared by the distortion of the tragedy Hotaru left behind――