Japan, soon before the start of a new era, 2019. Suddenly, a rip to another realm forms in the sky, showing "Shinkoku Nippon," an alternate planet with the sky and earth turned upside down. This alternative universe retains their past militarism, with Eternal Showa as its period. The military invades actual Japan with huge humanoid robots known as "Garann" and its gas weapons known as "Genmu," rendering our contemporary armaments useless. "Shinkoku Nippon" seizes the government and establishes de facto Japanese invasion. The "Reiwa" period has yet to come in Japan.