It is here that Osagami steps in, confronting the possessed person with only an empty scabbard and using his skills to battle the foe and sheath the sword, sealing in the evil and vanquishing them from this realm!
A new hate-filled killer is on the loose, and a rich Company President has been killed. The detectives are on the scene and among the spectators is Magazine Journalist Mio Mijo (Mai Fukagawa) who is trying to get an interview with them but is told practically nothing.
Seems the murdered man was the president of a company so Mijo goes to interview them and find out if he had any enemies. 
While doing the interview, she notices an assistant who comes in who seems to be giving off the same black clouds she saw before. What’s going ON?
Even after he's left, the tendrils of black swirl around in the air. She tries to take a photo of the mist, but nothing appears on camera.
Going out to the lobby, she sees the two curious men in black and confronts them. “You seem to be able to see the same black mist that I do…what IS it?” she queries, but they only tell her “If you see any black mists, RUN.”, which puzzles her even more.
That night, we find out why the assistant was emanationg such blackness- he is continuously persecuted by his boss and section chief. Day after day of them crushing his will and now he is a hateful person. Yes, he was the one who killed the president…and NOW, he’s going to kill his section chief!
Pulling out a dark hilt, he concentrates and a black blade materializes out of thin air!
Wielding it, he chases down the section chief, slashing at him and piercing his heart in the hallway!
The next morning, the detectives (along with Osgami and Iotsu) are looking over the security cameras, and it seems the section chief was killed by some invisible force! The killer is not tangible to such devices...but Osagami and Iotsu know what they're looking at.
Hearing the news of the Section Chief’s death, Mio is keen to dig deeper into the case and calls up the assistant she saw before for details of the murder. He tells Mio he’ll explain it all to her, but must be discrete and asks to meet up at a secluded warehouse….
The naive Mijo goes to the place on time, where the salaryman confesses to killing both the President and Section Chief…and intends to make this snoopy reporter his THIRD victim!
Mio flees and tries to put as much distance between herself and the the killer as best she can, but she stumbles and is about to be killed…
While they cart off the dead body, Mijo sees a curious black mist coming off the corpse which no one else seems to see.
Osagami and his partner Iotsu (Yuya Endo) are on the scene as well, taking note of the person murdered in order to track the killer. Mijo sees them and notices that they seem to see the black mist, too, but they offer nothing to her.
Wielding it, he chases down the section chief, slashing at him and piercing his heart in the hallway!
...when Osagami steps in and a dazzling sword/scabbard fight begins between the two!
Safely out of the way, Mio takes out her phone and tries to video record the fight...but, once again, the killer doesn't appear on the screen!
Things are even sided for awhile but Osagami gets the upper hand and manages to draw the blackness out of its host, capturing the sword into its sheath and reducing the former salaryman to a cloud of dark dust!
Mio cannot believe her eyes! What has she just been witness to? She once again tries to get the information out of the mysterious duo, but is told the same thing: “If you see the black mist, run away.”
Leaving the confused reporter behind, the two retreat back to their home base, where the dark sword is carefully boxed and sealed away... 
Must say, It's a nice change to see a supernatural-themed drama among this season’s picks, but a welcome one! Very interesting to watch with some TERRIFIC fight scenes and of course I LOVE Mai Fukahara and am delighted to see more of her!
It’s another job well done…but what is this black marking foring on Osagami’s arm? It seems all this dealing with darkness and evil may end up corrupting HIM as well.