|Also Known As||Kō (by an unnamed man)|
Ane-san (by Chūya Nakahara)
|Birthday||January 10 (Capricorn)|
|Likes||Kyōka Izumi, kinpura, pickles|
|Dislikes||Hope, love, Atsushi Nakajima|
|Manga Debut||Chapter 17|
|Anime Debut||Episode 17|
|Japanese Voice||Ami Koshimizu|
|English Voice||Cindy Robinson|
Kōyō is a tall and slender woman with cherry red eyes and red 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 hair clip and red ribbon which forms a five petal flower, and violet eyes.
Her kimono is pink overlapped by dark purple one with bell flower 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 her sword.
Kōyō holds herself with grace and dignity, but wastes no efforts hiding her dark nature. As a result of her failed escape from the Port Mafia, Kōyō is an extreme cynic, jaded against things like hope and love. Kōyō doesn't believe in the benefits of 'light', and claims that people born in 'darkness' are destined to never branch out for the light. With her eloquent speech, Kōyo often equates people to flowers. Some born in darkness, some destined to wilt. In her own words, "they [flowers] never have the chance to drop... if they remain mere buds", indicating she believes that no one will always remain pure, and that that purity is a waste compared to how they are when they fall. As a result, Kōyo both detests and fears 'light', thinking there's nothing but disappointment and despair once exposed.
Around her comrades, Kōyo maintains her composure, but has a much more laid back approach, and enjoys leisure time with her peers, such as the mafia's boss and her fellow executive. Towards others like Ace, however, she isn't the least bit subtle in her distrust, and comes off very passive aggressive.
After their hostility lowers, Kōyo extends some of her humour towards Atsushi Nakajima, but only once thus far, making a joke about how Osamu Dazai got information and cooperation out of her.
For all her grace, Kōyo's intense mindset leaves her prone to lashing out with cruel words and violent attacks - nothing out of the ordinary for a mafioso. Ruthless and brutal, Kōyo seldom holds back in a battle, only doing so for Kyōka Izumi's sake, and she is not above attacking when her target isn't looking.
Kōyo mentored Kyōka, consequentially being the cause of Kyōka's extreme fear of change when she first joins the Armed Detective Agency. For some time, Kōyo drilled a dreary, hopleless mindset into Kyōka to ensure she would never leave the mafia. She goes as far as to lie by telling Kyōka she's directly responsible for her own parents' murders, poisoning Kyōka's mind.
Claiming this to be only for Kyōka's well-being, Kōyo clearly projects her frustrations with life onto Kyōka. It takes Dazai's input for Kōyo to finally stop obsessing over Kyōka's defection, and let the girl grow and think for herself. Nonetheless, Kōyo's attachment to Kyōka drives her to infiltrate the Special Abilities Department, leaking the true events of Kyōka's past to the girl, and later makes a point of never physically harming Kyōka during the Cannibalism operation. This careful mindset extends somewhat to other detectives, however Kōyo only states that she dislikes the thought of harming Kyōka's friends.
Far from fearless, even Kōyo panics at the possibility of suffering through Dazai's infamous torture methods.
Kōyō has the ability to control the Golden Demon (金色夜叉, Konjiki Yasha?), a sword-wielding phantom. It is the same type of ability as Kyōka's, but she is able to control it with her own will.
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.
A year after Mori takes over the mafia, Kōyo is assigned to oversee (not necessarily mentor) Chūya Nakahara, after he joins the Port Mafia. As a result, Chūya answered directly to her much of the time. although she feels exasperated and too young to be called 'ane-san' by the boy, it's clear she later grows to accept it when she gets older.
Kōyō speaks to Ōgai Mori, who compliments the beauty of the falling flower petals. Although Kōyō agrees, she draws her blade, saying they'll never drop if they never bloom.
After locating Kyōka Izumi and Atsushi Nakajima, Kōyō calls Kyōka's cellphone, summoning Demon Snow to attack Atsushi. Making her appearance, Kōyō comments how even a pest's blood looks splendid, approaching Kyōka. When Atsushi tries to move, she stomps on his head, telling Kyōka it pained her to let the Agency "blind her" with its light.
She claims she's here to help Kyōka, and explains she went to the technician Atsushi mentioned earlier, killing him after modifying the cell phone's connections. Ignoring Kyōka's fear, Kōyō claims she's doing all for Kyōka's protection. When Atsushi shouts that Kyōka isn't returning to the Port Mafia, and that her powers are now meant for the Armed Detective Agency, Kōyō sheds a tear. She claims that she 'knew' she shouldn't have waited for Mori's orders to 'save' Kyōka from a "hive of deception and hypocrisy". She embraces Kyōka, saying that the Agency deceived her into thinking their world is filled with 'light', and points out that they Agency will eventually make her use Demon Snow, the ability she loathes so.
She promises to kill anyone who tries using Kyōka for her ability, making Atsushi lash out. Kōyō's Golden Demon lacerates him severely, and Kōyō mocks him, saying he's slow. Golden Demon impales Atsushi against a support beam, and Kōyō apologises, saying she's only doing her job. Upon seeing Kyōka's terrified expression, she calls Kyōka cute, and that she'd do anything for her, but Mori's orders are to eliminate all Agency detectives. She calls it war, with all Port Mafia leaders in agreement, sans Kyōka because of Kōyō's personal appeal on Kyōka's behalf.
She insists Kyōka must return to the Port Mafia, calling a flower than can only grow in darkness. Kyōka refuses, enraging Kōyō because she sees light in Kyōka's eyes. Blaming Atsushi, she brandishes her blade, threatening Atsushi's life if Kyōka doesn't return. Kyōka relents, agreeing to return with Kōyō, immediately calming the woman. Smiling, she releases Atsushi and says she does everything to Kyōka's sake, and that she'll understand someday.
Escorting Kyōka, Kōyō stops Kyōka from stabbing her with her bare hand, complimenting Kyōka's undetectable intent to kill. However, she's surprised to find out Kyōka stole her cellphone, and urges Kyōka not to use it to summon Demon Snow, she tries warning Kyōka what will become of her, but is cut off when Demon Snow appears. Both users and their abilities clash, and Kōyō exclaims that Kyōka's blade shows her true self - a demon that kills all in her way. She urges Kyōka to listen to her, saying she knows how she feels.
She expresses her belief in full detail - that flowers born in darkness can only thrive in it, and that the light's heat will burn it in the end, equating this to Kyōka, a 'natural born assassin' trying to be a good person. She recalls her attempt to run from the Port Mafia with a man, who ended up dying, relating the misfortune to Kyōka's current situation, and says the light burned and destroyed her.
Their battle rages on, and Kōyō continues to drill Kyōka's 'darkness' into her mind and heart. Saying Kyōka 'justifies' every massacre to achieve her goals, a nature that will never change. Otherwise, Demon Snow could never be a weapon, not to mention it 'killed' Kyōka's parents. The reveal greatly upsets Kyōka, who gives up resisting and allows Kōyō to take her from the Agency, who promises to protect her. Mafiosi arrive in cars to retrieve them, and Kōyō orders them to shoot Atsushi down.
Kenji Miyazawa and Doppo Kunikida arrive on the scene, saving Atsushi and angering Kōyō, who calls the Agency poison, yelling at them not to show Kyōka their "miasmic light". The clashing sides prepare for all-out war as a result. However, John Steinbeck and Howard Phillips Lovecraft interrupt the skirmish, alongside the arrival of other Guild fellowcrafts. Realising who they are, Kōyō orders mafiosi to fire and kill. Above, Mark Twain uses his ability to fatally injure everyone, including Kōyō.
Saved by Akiko Yosano's ability, Kōyō awakens to Atsushi and Osamu Dazai watching her in the infirmary. Unamused by Dazai's nonchalance, Kōyō asks him if he really thinks restraints can stop her, calling him a traitor that everyone in the Port Mafia wants dead. She asks Atsushi if Kyōka is safe, smiling and laughing darkly when told Kyōka's gone missing. Dazai stops Atsushi from attacking her, and assures him he'll deal with Kōyō himself. Kōyō refuses to divulge anything to Dazai, but complies when Dazai reminds her of how he used to help her torture squad, locking the door and making Kōyō panic.
Later, Atsushi confronts Kōyō, noting that she's kept in an unlocked room. Kōyō explains the 'lock' is within the mind, thanks to Dazai's interrogation. She guesses Atsushi is here to either finish her off, or just happened to enter her room after running away from a mistake on the front lines. Sensing that the latter is correct, Kōyō notes offhand that Dazai always picks the most difficult students. She then asks if Atsushi should be here, instead of helping Dazai.
Atsushi explains Dazai's speaking to a government agent, and Kōyō notes the Special Abilities Department would be a valuable aid to the Agency. Atsushi comments she's acting too nonchalant for a mafia executive. Kōyō agrees, summoning Golden Demon and saying she should kill Atsushi and report to Mori with this newfound information. She calmly dismisses Golden Demon, saying that's what she wants to say, but Dazai's prohibited any action on her part. She bashfully says Dazai did something 'unspeakable' to her, which she reveals to be a joke. She clarifies that she and Dazai simply made a deal. She's satisfied as long as Kyōka is found, claiming Kyōka will kill many people during this three-way conflict, forever unable to return to light, just as Kōyō hoped.
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.
The Guild Aftermath
With the Guild's defeat, Kōyō attends a meeting between Mori and Ace. Throughout the meeting, Kōyō openly expresses her disdain and distrust in A, questioning Mori's judgement on allowing him to investigate the mysterious man A's men retrieved.
Afterwards, Kōyō stole a transport truck of the Special Abilities Department's, attacking it disguised a a postman. She stole I-75-81, a classified report focused on Kyōka, intended to lesson the severity of her past crimes. 1-75-81 details Demon Snow and how Kyōka' parents truly died. Kōyō leaves it at the cafe when Kyōka isn't present,leaving no trace of her being the deliverer.
Upon her return, Kōyō run into Motojirō Kajii, who notes that Kōyō used half a year's worth of funds just to fulfill the task. Smiling, Kōyō says that her 'gift' to Kyōka 's acceptance in the Agency is a cheap price.
After Fyodor Dostoevsky poisons Mori, Kōyō guards his room. When Jun'ichiō Tanizaki infiltrates the room, Kōyō impale his chest, asking him to forgive her. With a dark expression, she says that without Mori, the Port Mafia will revert to its former state under the previous mafia boss, the same one that Kōyō attempted escape from. Tanizaki uses his ability in the battle, but Kōyō states that she can sense his bloodlust, and even though she dislikes the thought of harming Kyōka's allies, she has no choice for the Mafia's sake.
Kyōka saves Tanizaki's life, jumping out the window with him. Mafiosi attempt to shoot them down, but Kōyō orders them not, for they may shoot Kōyō . When they escape, Kōyō approaches the window, watching them with a downcast expression.
- Kōyō is one of the only characters to refer to Mori by his first name.
- The real life Kōyō Ozaki was male, whose real name is Tokutaro Ozaki (尾崎 徳太郎).
- In reality, Ozaki was the mentor of Kyōka Izumi, with the latter viewing Kōyō as a teacher even outside of literature.
- She shares her birthday with Yukichi Fukuzawa, on 10 January.