In his quest to find his lost companion, a young boy named Nai is ensnared by a captivating woman with a sinister appetite for human flesh. Simultaneously, Gareki, a resourceful thief, finds himself breaking into her opulent abode. When a commotion erupts, Gareki aids Nai's escape, only to confront the woman upon her return, triggering a chilling transformation into a monstrous entity. Fleeing in terror, the duo crosses paths with 'Circus,' a clandestine government unit tackling heinous crimes and shielding civilians from ravenous creatures called 'varuga.' Enticed by the promise of locating Nai's missing friend, they opt to enlist with Circus. Amidst their hazardous exploits, they square off against menacing varuga and delve into the enigmatic machinations of a shadow organization named Kafka.