Namaiki na Ryouken no Shitsukekata

From Bakeneko Scanslation:

The drug dealer Shinjuku police station’s detective Ao that was tracking for half a year was caught by a man that appeared suddenly. The problem is that Ao inhaled some of the evidence by accident. A young man by the name of Noe, helps Ao, who has lost consciousness after the fact. He’s reprimanded by his boss and receives sarcastic remarks from his co-workers. At that time Ao receives a photograph. That photograph shows a dead Naji, who was Ao’s S. It’s hunt or be hunted, eat or be eaten… the heated race of the yakuza men.