Seesaw Monster is technically two books in one, a dual novella collection where each story stands comfortably on its own while sharing a subtle connection. If you’ve read Kotaro Isaka before, you’ll recognise his signature blend of dark humour, kinetic pacing, and plots that reward patience. If this is your first encounter with him, it’s a reasonable starting point, though Bullet Train remains the more accessible entry.
The First Novella: Seesaw Monster
Set in 1980s Japan, the opening story centres on the external domestic battleground of the mother in law and daughter in law relationship. Except both women turn out to be former spies. The poor husband is caught between them, blissfully unaware of either woman’s past, which provides most of the dark comedy.
For me, this is the strongest of the two stories. The wife’s character development is genuinely compelling. Her transformation from quietly suffering spouse to someone reclaiming her formidable former self is the kind of arc that stays with you. The husband, meanwhile, becomes increasingly sympathetic simply by virtue of having absolutely no idea what is happening around him. The domestic tension escalates in ways that feel both absurd and oddly believable.
The Second Novella: Spin Monster
Set further in the future, the second story follows a courier in a world where digital communication has been so thoroughly compromised that sensitive information can only be trusted on paper. The now-elderly wife from the first story makes an appearance, which provides a satisfying continuity.
What makes Spin Monster genuinely interesting is its commentary on AI and information warfare. The central premise – that AI could directly inject fabricated news into media systems, manufacturing social unrest at scale – feels less like science fiction and more like an accelerated version of something already in motion. Isaka imagines paper documents becoming precious precisely because they cannot be hacked, and couriers becoming essential again for the same reason. It’s quietly unsettling inversion of progress.
The surveillance thread is equally chilling. Characters have cameras embedded in their eyes without consent, harvesting everything they see as data. Given that we already walk around with smart glasses capable of recording everything, the leap Isaka asks you to make isn’t as large as it should be.
The Part That Didn’t Work
The mythology of the Sea People and Mountain People, and ancient and recurring conflict between two groups predestined to clash across generations, is introduced as the philosophical backbone connecting both novellas. In theory, it’s an ambitious structural idea. In practice, it promises an epic clash and delivers what amounts to a family feud and a police investigation. The neutral mediator figure appears with significant narrative weight and then does very little with it.
If you strip out the Sea and Mountain People mythology entirely, both stories actually improve, in my opinion. The ideas are strong enough to carry themselves without the mythological scaffolding, which ends up feeling more like an imposed framework than an organic part of the narrative.
Final Thoughts
Seesaw Monster is an entertaining, thought-provoking read that works better as two separate stories than as a unified book. The first novella is warm and surprisingly moving. The second raises important questions about AI, surveillance, and the fragility of truth in a data-dominated world – questions that feel uncomfortably relevant right now.
Rating: 3.5 Muse Points. The Sea and Mountain People myth feels like Isaka reaches for something epic and lands somewhere merely interesting.
About the Author
Kotaro Isaka is a Japanese author and one of the most internationally recognised crime and thriller writers working today. He has won multiple major Japanese literary awards including the Mystery Writers of Japan Award and the Japan Booksellers’ Award. Fourteen of his books have been adapted for film or television, including Bullet Train which became a major Hollywood film.
