Kurata Yuki is staying alone at home while his parents are off on their vacation. His childhood friends Nekoyanagi Mei and Inui Sayo are helping him with the household stuff in the mean time. Mei is outspoken and active while Sayo is calm and knowledgeable. They have known each other for their entire life and they treat each other like they were real siblings. Little do any of them know, they’ll be involved in a love triangle a year from now.

Cicero City, a city infested with immigrants where people of all races scramble to find work and shelter. Infested with destruction and slaughter, it's a chaotic society. Living on the outside of society, the Jackals are professional assassins with no allegiance, available to the highest bidder. This is their story.
(Source: MU)

The story begins when the gods call a convention to decide the whether to let humanity live or die, and settle on destroying humanity. But a lone valkyrie puts forward a suggestion to let the gods and humanity fight one last battle, as a last hope for humanity's continued survival. 13 gods will fight against 13 human champions in one-on-one battles to decide whether humanity lives or dies.