POLICE DETECTIVE KYOICHIRO KAGA is a master in the Japanese martial arts discipline known as kendo. He has “strong” features, “keen and bright” eyes, and gives off “that very human sense of warmth.” He is an honorable man with no discernable character flaws, but is intensely private, occasionally grumpy, and wholly absorbed in his cases. A former schoolteacher, Kaga changed professions after his attempts to help one of his students who was being bullied ended in tragedy. He joined the police force, following in his father’s footsteps, and quickly became a rising star in the Tokyo Metropolitan Police Department’s Homicide Division until a complaint led him to be transferred out to the small “backwater” precinct of Nihonbashi. Inexplicably to his friends and colleagues, Kaga appeared content with his new assignment, even adjusting his style of police work to better accommodate the people he serves:

“You’ve changed since you got posted to Nihonbashi, Kyo. You’re really trying to blend in, to become part of the district. You know the place and the people who live here like the back of your hand.”

“The question is more how well you know me. I haven’t changed. You know what they say: ‘when in Rome, do as the Romans do.’ Applies to detectives too. You’ve got to adapt your style of working depending on where you’re posted.”

“I get that, Kyo, but you’re taking it to the next level.”

Kaga is the creation of the internationally best-selling author Keigo Higashino, whose work has won mystery awards in multiple countries and languages, and has been adapted for film and television in Japan. Of the nine Detective Kaga novels he’s written, only four have been translated into English: Malice (2014) by Alexander O. Smith and the remaining titles—Newcomer (2018), A Death in Tokyo (2022), and The Final Curtain (2024)—by Giles Murray. In the original order of publication, these are books four, seven, eight, and nine in the series, respectively. The decision by the publisher to release the series in this way is perplexing. While the English installments work well together (the Murray translations, in particular, form a consistent arc) the gaps left by the absent texts are still noticeable. Formative incidents in Kaga’s life, which are pivotal plot points in the early books, are summed up in a few sentences in later works for the sake of continuity. But such are the vagaries of translation.

While slightly frustrating, none of this diminishes the mastery of the novels we have access to. And while different in style, Smith’s and Murray’s translations work with their assigned texts, if not necessarily with each other. Malice is an outlier in the series and could easily be mistaken as a stand-alone title. It is completely unlike the other three in tone and narrative perspective. But, for better or worse, it is where English readers meet Detective Kaga for the first time.

Malice received rave reviews when it was released, not long after Higashino won an Edgar Award for the 2012 English translation of The Devotion of Suspect X (2005). However, very little of Malice’s success can be attributed to its “hero.” The Kyoichiro Kaga we meet in its pages is little more than an unassuming if ultimately brilliant foil to a charismatic killer. His suspect upstages him, using the first-person narration to give a virtuoso performance in obfuscation and misdirection. You could be forgiven for not recognizing Kaga as the book’s protagonist, let alone the main character of an entire series. And Higashino himself likely saw no reason to spotlight his star detective for a Japanese audience three books in. The true genius of Malice lies in its many twists, all instigated by the narrator. Like Kaga, readers have their suspicions that the narrator is the killer from the very beginning, but his testimony is so unreliable, so full of malevolence, that the extent of his guilt isn’t revealed or understood until the last chapter. It is the rare mystery that confounds the reader with a surprisingly simple and ultimately obvious solution.

Each Kaga book presents the reader with a unique, perfectly balanced puzzle. Higashino has stated that he has no set formula for his writing. “Some writers aim to move their readers, others want to write beautiful sentences. I want readers to be continually surprised by my ideas,” he told Andrew Joyce during a 2011 interview in which The Wall Street Journal compared him to Stieg Larsson. Higashino’s plotting is deliberate, meticulous, and layered. His characters use modern technology to solve golden age–style mysteries. Cell phones, tablets, DNA, and even Wikipedia confirm logical connections that have already been made.

Malice is a locked-room mystery in which everything is premised upon an unreliable narrator’s words. Newcomer, my favorite of the series due to its unusual structure, has Kaga interacting with and solving several small everyday mysteries for shop owners in Nihonbashi while assisting the homicide division in a murder investigation. In A Death in Tokyo, the Japanese tradition of leaving “senbazuru,” chains of a thousand origami cranes, at religious shrines becomes an important clue as to why a businessman is murdered on a bridge. And in the latest installment, The Final Curtain, Kaga must work through a tangle of false names and stolen identities to uncover multiple truths.

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The Final Curtain opens with the body of a middle-aged woman from the suburbs being found in an empty Tokyo apartment. The police soon learn that the victim, Michiko Oshitani, had traveled hours by train to surprise an old school friend she hadn’t seen in decades. Her family and colleagues have no idea why. And how she came to be in an apartment rented by a man named Matsuyo Koshikawa (who appears not to exist) is as much a mystery as who killed her. When the police are called to the site of a second murder, where a homeless man was killed and then set on fire, one of the detectives assigned to both cases suspects the deaths of Oshitani and the homeless man are related but needs to determine how. The narrator describes the moment “Matsumiya told his cousin about the Kosuge apartment. The atmosphere that filled the place: the absence of any sense of hope or dreams. The place was at once an apartment and not an apartment at all. It was a cramped space permeated with as much sadness as any blue-tarpaulin-covered homeless shack.”

Detective Shuhei Matsumiya is Kyoichiro Kaga’s cousin and a recurring character in the series. He lives with his mother, whom Kaga’s father helped support after Matsumiya’s father (Kaga’s father’s brother) died. They are Kaga’s only remaining family. The cousins are close, given their similar backgrounds, shared childhoods, and choice of careers. More than one of Kaga’s cases begins with Matsumiya coming to him for assistance, which Kaga gives under the condition that his cousin takes all the credit. So it’s no surprise when Matsumiya shares with his cousin his suspicions that the two deaths are somehow connected. But this time, the results are both unexpected and distinctly personal. A calendar was one of the few items in the apartment with Oshitani’s body. The names of 12 bridges have been written on its pages, a different bridge for each month. Kaga has a list, with the same bridges and months paired together, found among his mother’s effects after her death.

The detective’s relationship with both his parents is an arc revisited throughout the series, though significantly compressed in the English translations. Kaga’s mother abandoned him and his father when Kaga was nine. Sixteen years later, Kaga received a call informing him that she had died in a shabby apartment where she’d been living alone. There is no reason to suspect foul play. The cause of death was a heart attack. While he is able to learn some of the details of his mother’s life from her friend, much remains a mystery.

Hiromi Kadokura is also a mystery—alternately an actress, playwright, theater director, the old friend Oshitani was in Tokyo to see, and an acquaintance from Kaga’s past. She becomes the pivot point through which all aspects of the case connect. Her involvement in Oshitani’s murder and Kaga’s life becomes increasingly significant as her personal story unfurls. In many ways, she is reminiscent of the antagonist of Malice, minus the first-person narration, in that it has been her story we’ve been reading all along. We are privy to Kadokura’s inner thoughts in the same way we are privy to Matsumiya’s, via the close third-person narrator who moves between characters.

It’s hard to pinpoint the reason for the popularity of Kyoichiro Kaga, a character who sits on a pedestal separated from the rest of humanity. He is the one person in the series whose thoughts remain his own, whom we observe and learn about only through the eyes and ears of those around him. Yet he remains as impenetrable to them as he is to his readers. That might be the secret; perhaps Kaga is merely a mouse and Higashino’s true passion is the construction of ever more elaborate mazes. While that is a very real possibility, I prefer to believe he is ultimately the writer’s most complicated puzzle to date. And so he will remain. The Final Curtain ends moments before Kaga gets answers he has sought for decades. We already know what he is about to learn but are deprived of his reaction.

The Final Curtain is written in such a way that even readers with no knowledge of Kyoichiro Kaga can enjoy the mystery. Which is, to my mind, the best way to approach these books. For loyal readers, it satisfyingly ties up all the loose ends of Kaga’s family history, which have been hinted at and developed (albeit superficially) in the three preceding installments. It is unquestionably a fitting conclusion to a series enjoyed by millions of readers around the world. Higashino has said this will be the last Detective Kaga book, but those are famous last words. Regardless, for his English audience, there are hopefully more cases yet to be solved. Five, at the very least.