Ichiyō Higuchi/Synopsis

Armed Detective Agency vs. Port Mafia Arc
Higuchi contacts the Agency with a job, arriving at their office with the impression of a mild-mannered office worker. Tanizaki attempts to ask her what the job is, but Osamu Dazai interrupts with his usual waxing lyrical of beauty and requesting a "lovers' suicide" with him. Doppo Kunikida promptly shuts him down, and despite the commotion going on and Higuchi's rattled state, Tanizaki asks Higuchi not to mind them. Surprisingly, Higuchi gets right down to business - Tanizaki notices her 180 but assumes she's simply used to odd company.

Higuchi explains that some people of "low character" are hanging around behind her company's building. Kunikida asks her to clarify, and Higuchi answers that they're foreigners dressed in rags that skulk in the shadows. Kunikida concludes that they're smugglers, a given in any port city. Higuchi agrees, claiming that if she had evidence, she'd take the issue straight to the police, hence requesting the Agency perform a stakeout.

Higuchi leads Tanizaki, Naomi Tanizaki, and Atsushi Nakajima to the scene, ignoring their off-colour antics. She lures them into an alleyway, which, after learning Higuchi's name, Tanizaki notes as an odd place for smugglers to loiter, pointing out there's no escape route, and anyone would be trapped. Higuchi confirms his suspicions, suddenly putting her hair in a bun and unbuttoning her jacket. She confesses it to be "rude", but she's lured them into a trap. She calls Akutagawa, confirming her success and that she's "taking care of them" now. Drawing dual guns, Higuchi intends to kill them for the sake of her "overseer".

She opens fire, and Naomi shields Tanizaki from the barrage of bullets, collapsing covered in her own blood. Numb to Tanizaki's panic, Higuchi states they're aware Tanizaki's a "non-combative" ability user, "inviting" him to join his sister in death. Enraged, Tanizaki activates Light Snow, confusing Higuchi, who mistakes it as real snow.

Higuchi tries to mow him down, but with Light Snow as his cover, Tanizaki is essentially invisible to Higuchi. Undeterred, Higuchi attempts to blindly shoot in hopes of hitting him, assuming her bullets will hit him anyway. She misses entirely, and Tanizaki almost breaks her neck from behind. At that moment, Akutagawa severely wounds Tanizaki, essentially "saving" Higuchi.

Higuchi insists Akutagawa has to be mindful of his well-being and that she can handle the mission alone, to which Akutagawa snaps and slaps her. He points out that they're to take the weretiger alive, questioning what good killing them will do and calling Higuchi useless. Higuchi backs down with a meek apology.

She stays out of Akutagawa and Atsushi's battle, ordered to stay back when they realise the weretiger can regenerate, as it is nothing Higuchi can handle, further asserting her "uselessness" in the mission. However, when the weretiger lands a hit on Akutagawa, Higuchi disobeys him and attacks anyway, but her bullets do not penetrate the tiger's body. This directs the tiger's attention to Higuchi, but just before it kills her, Akutagawa slices it in half. It's revealed the tiger was a mirage of Light Snow, and Atsushi, the real tiger, again comes to blows with Akutagawa.

At that moment, Dazai suddenly appears, nullifying both ability users with No Longer Human. Higuchi demands how he found them, and Dazai reveals he slipped a tracking and recording device in her coat pocket during his little "lovers' suicide" tangent earlier. Disheartened, Higuchi realises Dazai saw through her the whole time. Nonetheless, she tries to stop Dazai from taking the others back to the Agency, but Akutagawa tells her there's no point.

Akutagawa's confidence in Dazai and Dazai's nonchalance irritate Higuchi, and she mocks Dazai as nothing more than an Agency detective, whereas the Port Mafia has a nigh endless supply of support and manpower, spanning from companies to political and economic branches. As a result, no one who defies Port Mafia lives to tell about it. None of this fazes Dazai, a former Port Mafia executive. With the mission failed and Dazai's arrival changing the game, Akutagawa and Higuchi are forced to retreat.

Only a day after a traumatising experience against Akutagawa, Atsushi learns of Black Lizard, a battalion squad of the Port Mafia operating directly under Akutagawa and Higuchi. Aware of the bounty of his head and the Port Mafia's ruthless methods, Atsushi decides to contact the Port Mafia himself. Higuchi answers the call, at first shocked he was able to contact her until she recalls leaving a "business card" during her failed mission. Higuchi notes the Agency saved Atsushi this time but vows he won't be lucky next time. To her shock, Atsushi proclaims he's leaving the Agency, which Higuchi understands to mean the Port Mafia targets him, instead of endangering the Agency.

Sceptical, Higuchi orders a summons for Black Lizard. Ryūrō Hirotsu later contacts her, and Higuchi states their mission is to destroy the Agency's office. Higuchi reasons that they failed to obtain the mantiger because of the Agency's involvement, and they must be eliminated first. Hirotsu asks if they're to kill everyone, to which Higuchi simply tells Black Lizard to "do as they will". Hanging up, Higuchi scowls in deep-seated anger, recalling how Akutagawa backed down in Dazai's presence, which enrages her, and she won't stand for it.

Higuchi does not take action for the rest of Atsushi's bounty until after Akutagawa's brutal defeat. Using a motorboat, she discovers Akutagawa's unconscious, gravely injured body floating in the ocean. She's quick to rescue him and get him the medical attention he needs.

She faces Ōgai Mori, Port Mafia's infamous boss. Mori sums up Akutgawa's dire state, offering no sympathy for his failure, and calmly points out he may remain comatose for good, much to Higuchi's dismay. Mori assures her she needn't be discouraged, as they both did their best despite failure, stating "effort is what matters, results come second". Unsurprisingly, his "encouragement" does little to reassure Higuchi.

Mori informs her that "Karma Transit", the smuggling group Akutagawa massacred, are regrouping, intent on exacting revenge against Akutagawa. Mori equivalates Port Mafia's violence as a sort of "currency" for economic gain, but for someone to retaliate against them is a liability they cannot afford. As in, Akutagawa is a liability, to which Higuchi points out Akutagawa's remarkable capabilities and contributions, Mori doesn't deny his efforts. However, he questions Higuchi's place in Port Mafia, shutting down her argument.

Having been dismissed, Higuchi tries to recollect herself in the restroom, soon interrupted by Gin, who appears behind her with a knife to her throat. The remaining two Black Lizard members, Hirotsu and tachihara, come to confront Higuchi, warning her that she's contemplating a huge risk.

Hirotsu points out that she and Akutagawa command a group that answers only to Mori, holding authority over a squad like Black Lizard. However, their titles aren't what makes Black Lizard obey - it is Akutagawa's fearsome ability and temper. With Akutagawa out of commission, Hirotsu questions what Higuchi has to compel Black Lizard to obey her.

Frustrated, Higuchi visits Akutagawa, remembering an earlier incident where he continually rejected her assistance, his one-track mind obsessed with gaining Dazai's attention. As usual, Akutagawa's stubborn refusal of her assistance leaves Higuchi distraught. Higuchi returns home, slumping to the floor and remembering Mori's question. Higuchi admits she has no place in Port Mafia.

Soon after, Higuchi is informed Akutagawa's been captured, as Mori anticipated. Against Mori's orders, Higuchi makes a move, but Hirotsu urges her to reconsider. Higuchi ignores him, only for Tachihara to try stopping her as well, going as far as grabbing her arm to hold her back. He points out "Karma Transit" hired mercenaries, of which Higuchi can do nothing against alone, and she should just wait for Mori to give the order to save Akutagawa. Higuchi yanks away, shooting him a harsh look, stating that that order will never come.

Higuchi understands that if the Port Mafia involves themselves, it'll spread into an all-out turf war with other groups, so the higher-ups want it to stay under wraps as a "squabble" between individual agents, calling Akutagawa a "sacrifice" in their eyes. Higuchi's aware she can't do anything on her own, but she can't just stand around and do nothing. She runs off, remembering how flustered she gets for missions, knowing she isn't fit for the Port Mafia. She admits contemplating trying to leave, even if it isn't easy, but the only thing that stopped her was her devotion towards Akutagawa.

Making it to the mercenaries' hideout, she fights off her fears, throwing a bomb before going in guns blazing against them. She is quickly outmanned and overpowered, injured by a bullet through her thigh. She knows she can't fight like this, but persists for Akutagawa's sake. Just then, Black Lizard bursts through, providing assistance. At Higuchi's disbelief, Hirotsu reasons that as their commanding officer, Black Lizard cannot stand by when she's in trouble, mirroring Higuchi's resolve to save Akutagawa.

Higuchi reunites with Akutagawa, who weakly apologises to her. With tears in her eyes, Higuchi assures him she's just doing her job.

The Guild Arc
Higuchi and Gin work together in tracking Dazai, later confronting him when he's isolated. Higuchi gives Dazai a message directly from Mori: a return to his seat as a Port Mafia leader. Dazai's surprise is short-lived, and his fit of laughter catches Higuchi off guard. Higuchi points out she's looked into Dazai's records, well aware of how cruel and blood-stained his past is. She goes as far as saying that his blood is "as dark as the mafia itself", claiming he is darkest than anyone else in Japan.

Dazai brushes her claims off, derailing the conversation from himself and to Gin, leading to the first time Higuchi realises Gin is a girl, surprised at her cute voice.Dazai questions why Mori would bother sending personnel after him, and Higuchi's quick to correct him. After Kyūsaku Yumeno's release, Higuchi and Gin are tasked with "protecting" Dazai, whom the child harbours a grudge against. Dazai attempts to deny such a statement, but Higuchi points out Mori will use any possible option to eliminate the Guild. Quick to understand why Higuchi and Gin are meant to "protect" Dazai, he rushes off, leaving an unfazed Higuchi.

Later, while Higuchi remains largely uninvolved in the Guild war, it's revealed that after receiving information from Dazai, Hirotsu informed Higuchi of the Moby Dick infiltration. True to her nature, Higuchi then informed Akutagawa, leading to his solo mission on the Moby Dick, all part of Dazai's plan to form the new "Twin Dark" against a looming threat.

The Guild Aftermath Arc
Following the three-way conflict, while driving down at night, Higuchi notices Akutagawa in his civilian clothing along the streets. As she thinks of a way to drive him home, she sees a woman leaving with him, much to her distress.

The next day, Higuchi tries to look for the woman, thinking that she is either an enemy assassin or a government spy sent to harm Akutagawa. She is later found by Kunikida and Atsushi, who think she is spying on them amidst the ongoing ceasefire between the Agency and the mafia. To their surprise, Higuchi asks to tell her everything about the woman on the photo they are looking for.

Higuchi supports the two Agency members in finding the woman, thinking that Atsushi will give her a love letter, which she then thinks can "break up" the woman and Akutagawa. Katai Tayama catches up to them and clarifies that he is the one confessing, much to Higuchi's disbelief. They eventually find the woman coming out of a laundromat, after which Higuchi and Katai chase her. Reaching a dead-end alley, Higuchi finally recognizes the woman to be Gin, and they also learn that she is Akutagawa's younger sister, to which Higuchi sobs out of relief. Later, she asks Gin to call her "older sister" as her superior.

Cannibalism Arc
After Fyodor Dostoevsky stabs Mori, infecting him with Alexander Pushkin's virus, Higuchi is the first to rush in and aid Mori. Naturally, she participates in the Port Mafia and Agency's feud. While patrolling their headquarters, she is ambushed by Kyōka's Demon Snow, dragged into another room. Kyōka threatens her for the security code of Mori's safe room.

Undeterred, Higuchi notes how it seems Kyōka hasn't sworn off killing as records claimed. Kyōka responds that she doesn't kill idly, instead of warning Higuchi that if she doesn't answer, Demon Snow will cut off Higuchi's hand. With a bitter smile, Higuchi notes that she's been prepared for such an incident since joining Port Mafia. However, just before Kyōka can do anything, Akutagawa intervenes, cutting a hole in the floor and separating the two. He instructs Higuchi to alert the others of the Agency's raid.

As the situation worsens, Higuchi orders everyone to stop frontal assaults, alerting them that Mori disappeared. Hirotsu arrives, informing her that there's word bodyguards saw Mori leave of his own volition. Higuchi questions Mori's decision, but Hirotsu alludes that this may be Mori's way of protecting Port Mafia.

Befitting of the Port Mafia's major mafiosi, she arrives to confront Pushkin after his defeat.

Decay of Angels Arc
Since Akutagawa's disappearance after boarding the Boswellian, Higuchi prepares a funeral for him. Two days later, she apparently receives a letter and finds Akutagawa without his coat. She rushes to him and confesses her feelings for him, admitting that she now knows that she does not wish to end everything without imparting some words to him. Before she can finish, an apparently undead Akutagawa turns around and bites her, infecting her with Bram Stoker's ability.

Eventually, the turned Higuchi attends a mafia meeting and bites Gin, turning her into her kind. Hirotsu tries to attack Higuchi, only for the latter to immediately overpower him with her strength. In turn, Gin bites Hirotsu and turns him to their kind, instructing Tachihara to escape immediately.