The protagonist - Usui Yoshihito works at Shinoda Shinjuku Detective Agency.

The agency received a classified assignment from the Shinjuku Central PD.

A joint-investigation behind the wide-spread drug smuggling route within Shinjuku area.

His partner from the police department, Agumo is a diligent detective.

Having a shady past, he feels umcomfortable working with Agumo,

but the job itself is right up his alley.

Soon, the undercover operation begins.

In the meanwihle, he encounters a mafia named Hata, who seems to know Usui's past...