Beneath the tranquil streets of Fukuoka lies a treacherous underworld, brimming with hitmen, detectives, and individuals with an insatiable thirst for vengeance. Among these inhabitants is Zenji Banba, a composed and astute investigator delving into the nefarious activities of mercenary groups in the vicinity. But Banba is not alone in his antipathy towards these syndicates; Xianming Lin, a male assassin in disguise, is disgruntled by his paltry earnings and the dearth of job opportunities. When Lin's latest target chooses to end his own life, his employers renege on their promise to compensate him. Nonetheless, Lin is unyielding, and accepts the task of assassinating Banba, whom they believe is meddling in their affairs. However, when Lin arrives at Banba's abode, he shocks him by proposing that they work together instead of killing him. Banba is now faced with a daunting decision: what are Lin's true motives for the criminal landscape of Fukuoka?