Tatsumi is a self-acknowledge country bumpkin who is nonetheless a well trained fighter. He and two companions leave their remote village to head to the Imperial City to find a way to relieve their friends and family from ruinous taxation imposed by the authorities. Yet the Imperial City is filled with unimaginable amounts of corruption and evil from supernatural sources. Tatsumi is immediately swindled after reaching the City and nearly loses everything soon after, but finds himself allied with an unlikely group of assassins.
One day, the moon exploded, leaving it in a perpetual crescent-moon shape. The creature who claims responsibility for the destruction also claims it will destroy the world in March of next year. With powers beyond human comprehension, no military can stand against it. Yet, for some reason, it chooses to take up occupancy as a teacher in the worst class of Kunugigaoka Middle School. The fate of the world rests in the hands of its students, as they have until graduation to figure out how to murder their teacher and collect ten billion yen for saving the world.
Toru Acura is a 20-year-old retired soldier meandering through life now that the war has ended. He encounters Chaika Trabant, a 14-year-old sorceress carrying a coffin, and follows her in hopes of finding meaning to his life again. The two travel with Toru's adopted sister, Akari, the employed member of the group and thus Toru's source of income.
At first glance, Arashi Mikami appears to be a normal, albeit socially awkward, 17-year-old high school student. He's actually part of a secret vigilante organization known as Black Label, a group dedicated to executing power-hungry criminals the law refuses to deal with. However, taking down a crime lord isn't always an easy task, and there are bound to be consequences for any action...
This is the action-packed story of the trials of Arashi and the people close to him.