Kōyō Ozaki

Kōyō Ozaki (尾崎 紅葉,) is a Port Mafia executive and has the ability Golden Demon.

Appearance
Ozaki appears as a tall and slender woman with pink hair tied into a traditional Japanese bun that is held by three long golden clips and another hair clip on the right side of her head, composed by a light pink furry hairclip and red ribbon which forms a five petal flower, and violet eyes. She dons what seems to be a traditional Kimono tied in a bow, covered under a light-purple mantle. She also wears a pair of brown shoes.

In the anime adaption, Kōyō has red eyes and red hair, but she still retains her manga hairstyle. Her kimono is pink overlapped by dark purple one with red spider lily motifs, tied neatly with a maroon bow which has white borders, and a light pink mantle which goes darker in color from her elbow to her feet. She wears red eye shadow and light pink lipstick.

Kōyō carries a red Japanese umbrella which conceals a sword with silver blade.

Personality
Ozaki comes off as a mature, serious, emotional and cruel woman.

At first, it looks as if she were only obsessed with Kyouka, going to such lengths of attacking Atsushi and claiming to kill him and any other who dares to 'show her the light', only for Kyouka to be by her side once again: and even torturing her psychologically to ensure this. Despite that, she has shown to genuinely care about her being - going as far as to plead Ougai on sparing her, showing no resentment after being deceived and attacked by her, and asking Atsushi about her welfare after being beaten by The Guild.

Ability
Kōyō has the ability to control the Golden Demon (金色夜叉,), a sword-wielding phantom. It is the same type of ability as Izumi Kyouka's, but she is able to control it with her own will.

Background
When young, she tried to leave the Mafia together with a man whom she admired. Nevertheless, they were caught and the man was killed. Since then, she has held a grudge only against the Mafia's former leader who did those heinous acts.

Sometime in her past, it is assumed she took in Chuuya when he was young and raised him.

Plot
Kōyō first appears to retrieve Kyouka Izumi from the Armed Detective Agency, warning her that the light Atsushi Nakajima shows her is unfit for a "flower born in darkness" such as herself. She uses Golden Demon to severely injure Atsushi, threatening his life to force Kyouka into agreeing to return to Port Mafia with her. However, when Kyouka attempts to stab her, the two clash with their similar abilities.

Minor Port Mafia members appear in assistance, as do Doppo Kunikida and Kenji Miyazawa appear for Atsushi and Kyouka. However, John Steinbeck and H.P. Lovecraft interrupt the skirmish, with Mark Twain using his ability to fatally injure everyone.

Kōyō survives, having receive d treatment for her wounds, but her poor condition leaves her in the ADA's custody. She wakes up, and, much to her shock, comes face to face with not only Atsushi, but Osamu Dazai.

When she hears of Kyouka's disappearance, she smiles darkly, angering Atsushi. However, Dazai stops Atsushi and tells him he can handle the woman on his own. Although reluctant to divulge any of Port Mafia's secrets to Dazai, the former reminds her that their unit would always refer to Dazai for particularly gruesome tortures of prisoners. When Dazai threatens such torture on her, Kōyō's reluctance severely wavers.

They converse, discussing Kōyō's cynicism over Kyouka's joining the ADA, to which Dazai comments the darkness Kōyō so strongly believes in is personal to her thanks to losing a loved one when attempting to run from the mafia prior to Mori's reign. Ultimately, it is Kyouka's well-being that persuades Kōyō to inform Dazai on what the Port Mafia knows.

Later, Kōyō is freed from the ADA and returns to Port Mafia, which suffered great casualties after The Guild kidnapped and manipulated Q's ability. She gives Mori a letter straight from Dazai, which urges the ADA and Port Mafia to enter a ceasefire to defeat the Guild.

Trivia

 * The real life Kōyō Ozaki was male, whose real names was Tokutaro Ozaki (尾崎 徳太郎).
 * In reality, Ozaki was the mentor of Kyouka Izumi, with the latter viewing Kōyō as a teacher even outside of literature.