Yuu Enji knows that adults are vile and hateful beings. After enduring his father's abuse, he later found solace in his group home, where he gained a family that truly mattered: his fellow orphans.

Now, Yuu is about to graduate high school, and since his academics are lacking, he is set on immediately entering the workforce and amassing enough money to purchase his orphanage. However, before he can begin to put this plan into action, tragedy strikes the entire world. All the adults in existence are transformed into monstrous roosters and chickens, whose only desire is to devour every child in sight.

Nothing matters more to Yuu than his precious siblings, but faced with towering birds who lust for guts, will he be able to escape this culling with his family intact?