Memento Scarlet

From Exiled Rebels Scans:

Amane Kairi is a lecherous but capable detective part of the Special Police Force. In one of their most recent cases, they have come across a drug dealer who is only known to wear a red coat. Kairi goes to look for the help of a problematic ex-detective by the name of Kanoo Tetsuo. After retiring from the police force, Tetsuo has begun to investigate “the man in red” by himself, not knowing that he will be pulled back in by the alluring Kairi.