Seesaw Monster by Kotaro Isaka

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Seesaw Monster by Kotaro Isaka - July 2025

Kotaro Isaka has built his reputation on a foundation of kinetic action, darkly comic dialogue, and labyrinthine plots that converge with mathematical precision. From the international success of Bullet Train to the philosophical violence of Three Assassins, Isaka’s works consistently blend high-octane thrills with deeper meditations on fate, conflict, and human nature. In Seesaw Monster, translated with nuanced precision by Sam Malissa, Isaka attempts his most ambitious narrative structure yet: a dual-timeline exploration that spans decades while examining the eternal nature of human discord.

The result is both his most intellectually challenging work and, paradoxically, one that occasionally struggles under the weight of its own mythological ambitions.

Two Eras, One Ancient War

Seesaw Monster operates across two distinct time periods, connected by the enigmatic concept of an ancestral feud between “Sea People” and “Mountain People.” In 1980s Japan, pharmaceutical salesman Naoto finds himself caught between his feuding wife Miyako and mother, whose animosity seems to transcend ordinary family tension. When a mysterious insurance salesman named Ichio Ishiguro introduces the mythology of ancient bloodline conflicts, their domestic warfare takes on cosmic proportions.

Decades later, in a near-future Japan dominated by surveillance technology and facial recognition systems, courier Naomasa Mito navigates a world where paper documents have become the only truly secure medium for sensitive information. When Mito encounters his childhood nemesis Kagetora Hiyama—now a police detective—on a routine delivery, both men are drawn into a conspiracy that echoes the ancient patterns of conflict their predecessors experienced.

Isaka’s decision to structure the narrative as parallel stories rather than a straightforward chronological progression demonstrates his continued evolution as a storyteller. The 1980s timeline captures the economic optimism of Japan’s bubble era while exploring intimate family dynamics, while the future timeline presents a techno-thriller examining privacy, surveillance, and the persistence of human nature in an increasingly digital world.

The Mythology of Inherited Conflict

At the heart of Seesaw Monster lies Isaka’s most philosophically ambitious concept: the idea that some conflicts are not personal but archetypal, passed down through bloodlines like genetic predispositions. The Sea People versus Mountain People mythology functions as both plot device and thematic framework, suggesting that certain antagonisms are as inevitable as gravity.

This concept works most effectively in the 1980s storyline, where Miyako and her mother-in-law’s relationship provides concrete emotional grounding for abstract mythological concepts. Their collaboration on the children’s book “I Am Mai-Mai”—featuring a snail with the Lance of Longinus—becomes a poignant metaphor for finding creative solutions to seemingly irreconcilable differences. Isaka demonstrates particular skill in depicting how two people can simultaneously despise and depend on each other, creating something beautiful through their very opposition.

The future timeline’s exploration of this theme proves more problematic. While Mito and Hiyama’s mutual revulsion is viscerally portrayed, their connection feels more manufactured than mythic. The revelation of their shared trauma from a childhood car accident provides psychological justification for their antagonism, but undermines the supposedly supernatural nature of their conflict. Isaka seems uncertain whether he’s writing science fiction, mythology, or psychological realism, and the narrative suffers from this indecision.

Technical Mastery Meets Conceptual Ambition

Sam Malissa’s translation deserves particular recognition for maintaining Isaka’s distinctive voice while navigating complex temporal shifts and mythological concepts. The dialogue crackles with Isaka’s characteristic wit, particularly in exchanges between Chusonji and Mito, where philosophical concepts are debated with the casual intensity of discussing baseball statistics. Malissa captures the subtle differences in language between eras without resorting to heavy-handed period markers.

Isaka’s world-building in the future timeline demonstrates impressive attention to detail. The society where digital information is inherently insecure, making analog couriers essential, feels both plausible and satirical. The author’s background in mystery writing serves him well in constructing the surveillance apparatus that drives the plot, creating genuine tension as Mito attempts to navigate a world where every movement is monitored.

However, the novel’s pacing suffers from its structural ambitions. While individual scenes maintain Isaka’s trademark momentum, the constant temporal shifts disrupt narrative flow. Readers invest emotionally in one timeline only to be abruptly transported to another, creating a sense of narrative whiplash that undermines both storylines’ effectiveness.

Character Development and Emotional Resonance

Isaka’s characterization shows notable growth in complexity compared to his earlier works. Miyako emerges as the novel’s most fully realized character, a woman whose sharp wit masks profound loneliness and whose creative collaboration with her enemy reveals unexpected depths of empathy. Her evolution from antagonistic daughter-in-law to elderly sage provides the novel’s emotional anchor.

Naomasa Mito represents Isaka’s attempt to create a more introspective protagonist than his usual action heroes. Mito’s car phobia and trauma-induced memory distortions add psychological complexity, but sometimes feel like authorial mechanics rather than organic character development. His relationship with girlfriend Hinata provides necessary emotional grounding, though she occasionally serves more as philosophical mouthpiece than fully realized character.

The supporting cast maintains Isaka’s talent for creating memorable eccentrics. Atsushi Chusonji, the tech-savvy fugitive who becomes Mito’s reluctant ally, delivers some of the novel’s funniest lines while serving as exposition machine for the technological aspects of the plot. Detective Hiyama’s rigid adherence to rules provides effective contrast to Mito’s growing flexibility, though his character feels somewhat schematic.

Thematic Richness and Philosophical Depth

Seesaw Monster succeeds most completely in its exploration of how conflict can be simultaneously destructive and creative. The children’s book collaboration between Miyako and her mother-in-law suggests that opposition itself can generate beauty, while the technological cat-and-mouse game in the future timeline demonstrates how conflict drives innovation and adaptation.

Isaka’s meditation on memory and truth proves particularly compelling. Mito’s discovery that his memories of the childhood accident may be fundamentally distorted raises questions about the nature of identity and responsibility. If our understanding of formative events is unreliable, how do we construct meaning from our experiences? The novel’s suggestion that multiple versions of reality can coexist simultaneously feels both philosophically sophisticated and dramatically satisfying.

The surveillance theme resonates powerfully in our current moment, though Isaka avoids heavy-handed commentary. Instead, he focuses on how constant monitoring changes human behavior and relationships. The world where only handwritten messages provide privacy feels like logical extrapolation rather than dystopian warning.

Literary Ambitions Versus Genre Expectations

Seesaw Monster represents Isaka’s most literary work, prioritizing thematic development over pure entertainment value. This shift will likely divide readers familiar with his more straightforward action novels. The philosophical weight occasionally threatens to overwhelm the narrative momentum that made works like Bullet Train so compulsively readable.

The novel’s exploration of mythological themes positions it more clearly within the tradition of contemporary Japanese literature that blends realism with supernatural elements. Authors like Haruki Murakami and Banana Yoshimoto have explored similar territory, though Isaka’s approach feels more systematic and less dreamlike than his literary compatriots.

Minor Flaws in Major Ambitions

Despite its considerable strengths, Seesaw Monster suffers from several structural and conceptual problems. The dual timeline structure, while thematically appropriate, creates pacing issues that prevent full emotional investment in either storyline. The mythological elements, while fascinating, never quite achieve the resonance that would elevate them from clever plot device to profound truth.

The novel’s ending, while providing narrative closure, feels somewhat anticlimactic given the build-up of ancient conflicts and technological conspiracies. Isaka seems more interested in exploring his concepts than in providing the explosive resolution his previous works have delivered.

Some supporting characters feel underdeveloped, particularly in the future timeline where the conspiracy elements sometimes overwhelm character development. The balance between action and reflection that Isaka has mastered in previous works occasionally tips too far toward contemplation.

Recommendation and Context

Seesaw Monster will most appeal to readers who appreciate Isaka’s intellectual ambitions and are willing to accept a more measured pace in exchange for thematic complexity. Fans of his pure action works may find themselves occasionally impatient with the philosophical digressions, while readers seeking profound literary insight may question whether the genre elements support or distract from the deeper themes.

The novel works best when considered alongside other contemporary works exploring technology’s impact on human relationships and the persistence of ancient patterns in modern life. Readers who enjoyed the mythological elements might also appreciate The Tale of the Bamboo Cutter by Donald Keene or The Memory Police by Yoko Ogawa for their blend of the fantastic and the philosophical.

For those new to Isaka’s work, Bullet Train or Three Assassins provide more accessible entry points to his distinctive style. Seesaw Monster represents the author stretching beyond his comfort zone, with mixed but ultimately rewarding results.

Final Assessment

Seesaw Monster stands as Kotaro Isaka’s most ambitious and uneven work. While it doesn’t achieve the perfect balance of entertainment and depth that characterizes his best novels, it succeeds in expanding his thematic range and demonstrating his continued growth as a writer. The novel’s exploration of inherited conflict, technological surveillance, and the creative potential of opposition provides rich material for contemplation, even when the execution doesn’t quite match the conception.

Sam Malissa’s translation ensures that English-speaking readers can fully appreciate both Isaka’s linguistic playfulness and his philosophical seriousness. Despite its flaws, Seesaw Monster confirms Isaka’s position as one of contemporary crime fiction’s most intellectually adventurous practitioners.

In an era where genre boundaries continue to blur, Seesaw Monster represents a meaningful contribution to the conversation about how popular fiction can address serious themes without sacrificing its essential entertainment value. While not entirely successful in its ambitious goals, it suggests fascinating directions for Isaka’s future work and provides plenty of material for readers willing to engage with its complex ideas.