Gyakuten Sekai no Denchi Shoujo S01

Japan, 2019, just before the dawn of a new era. Suddenly, a rift to another dimension appears in the sky and reveals an alternate world called "Shinkoku Nippon - Real Japan", where the sky and earth are inverted. This parallel world retains its former militarism, and this era is exactly like the "Showa - 1926" era in Japan. The army, with giant humanoid robots called "Garann" and gas weapons called "Genmu", attacks the original Japan and renders our modern weapons ineffective. "Shinkoku Nippon" immediately takes over the government and conquers Japan. The new "Reiwa - 2019" era has not yet arrived in Japan.