Koudo Ikusei Senior High School is a leading prestigious school with state-of-the-art facilities where nearly 100% of students go on to university or find employment. The students there have the freedom to wear any hairstyle and bring any personal effects they desire. Koudo Ikusei is a paradise-like school, but the truth is that only the most superior of students receive favorable treatment.
Ayanokouji Kiyotaka is a student of D-class, which is where the school dumps its "inferior" students in order to ridicule them. For a certain reason, Kiyotaka was careless on his entrance examination, and was put in D-class. After meeting Horikita Suzune and Kushida Kikyou, two other students in his class, Kiyotaka’s situation begins to change.
Japan, 2019, just before the dawn of a new era. Suddenly, a rift to another dimension appears in the sky, revealing an alternative world "Shinkoku Nippon," with the sky and the earth upside down. This parallel world keeps the former militarism, with its era being Eternal Showa. The military invades the real Japan with giant humanoid robots called "GARANN" and their gas weapons "GENMU", rendering our modern weapons ineffective. "Shinkoku Nippon" instantly seizes the government and achieves de facto conquest of Japan. The new era, "Reiwa," has not arrived for Japan.
At Kamome Academy, rumors abound about the school's Seven Mysteries, one of which is Hanako-san. Said to occupy the third stall of the third floor girls' bathroom in the old school building, Hanako-san grants any wish when summoned. Nene Yashiro, an occult-loving high school girl who dreams of romance, ventures into this haunted bathroom...but the Hanako-san she meets there is nothing like she imagined! Kamome Academy's Hanako-san...is a boy!