The monstrous enemies of humanity are steeped in mystery, but that won’t stop us from theorising about their origins.
Kaiju No.8 wowed battle shonen fans when it aired in 2024 with fast-paced action, a compelling main character in Kafka Hibino, and most importantly of all, some incredibly gnarly monster designs. The anime is set in an alternate reality version of Earth where monsters, referred to as kaiju, run amok in the futuristic remnants of Japan. These kaiju are incredibly deadly, and have caused near world-ending destruction at various points in time.
But what are they, exactly?
The anime and manga don’t exactly go into the origins of these kaiju, nor how they ended up wreaking havoc as humanity’s number one enemies, as the manga artist, Naoya Matsumoto, has yet to confirm the origins of kaiju even with the manga reaching its end. What we do know is that the kaiju have existed well back into recorded history, where even Samurai battled to the death against these threats in the Meireki era (1655-1658).
Warning: Spoilers ahead!
What are kaiju in popular culture, and what does Kaiju No.8 have in common with them?
In Japanese film history, the concept of kaiju took form when the iconic monster Godzilla was first introduced to the masses in its eponymous film in 1954.
Godzilla has since been established to be a prehistoric reptilian or dinosauric monster that lived within the ocean depths, and was awakened and empowered by years of radiation due to the aftereffects of nuclear bombing and testing. Later on, the term kaiju, which literally translates to ‘strange beast’, was used as a catch-all term to categorise giant movie monsters even outside of Japanese film.
It’s confirmed in a Weekly Bunshun interview that Naoya Matsumoto was inspired by Hideaki Anno’s uniquely monstrous iteration of Godzilla in the 2016 movie ‘Shin Godzilla’, specifically the link it drew between kaiju and natural disasters.
The theories:
The kaiju in Kaiju No.8 are living beings superpowered by natural selection
The manga confirms in Chapter 58 that recent studies into kaiju biology have given credence to a theory that the immense energy and strain produced by faults in the earth have affected underground substances, plants, and animals to produce kaiju. In that sense, earthquakes, and the seismic energy it produces, significantly impact biological evolution through dramatic environmental changes that drive natural selection and speciation.
It does make some kind of sense. The kaijus are primarily a threat due to their biological capability–they are immensely strong, can rapidly evolve to gain human levels of intellect, and can generally survive any type of attack given that their kaiju cores remain intact.
But their semblance to biological life stops there. A key characteristic to consider a creature biological is if they have the ability to reproduce, and it seems that the kaiju in Kaiju No.8 have no solid means of reproduction, asexual or otherwise. The creatures seemingly spawned out of nowhere, and, save for Kafka who was transformed, can only multiply through proliferation through a honju's corpse. This leads into another theory:
Kaiju are man-made creations–but not like how you think
This theory doesn’t really hold much weight based on what the manga has explicitly confirmed, but ties in with the origins of the concept of kaiju in our world. Various circumstances in the story, specifically with how Kafka was transformed by the mysterious larva kaiju, point to this possibility.
The mysterious larva, which debuted in Chapter 1, is an amalgamation made from the fallen samurai and warriors during the battle against the daikaiju of the Meireki era (Chapter 117), leading to its decision to fuse with Kafka and use him as a vessel to destroy all kaiju.
This also ties in with a specific 2001 Godzilla movie, ‘Godzilla, Mothra and King Ghidorah: Giant Monsters All-Out Attack’, where Godzilla is depicted as a vengeful spirit who was reanimated and possessed by those who were killed during World War II.
There’s a metaphysical and nigh-fantastical factor to this theory, leading to a hypothesis that the kaiju may have been formed due to extreme feelings such as rage or regret. In the manga, the core for the mysterious larva was formed from the heart of a dying samurai who fell into a chasm, and whose soul acted as an anchor for his fellow warriors’ collective anger.
Considering the previous theory, but abandoning its naturalistic basis, the abundant seismic energy of the chasm could have helped in the generation of the kaiju core by strengthening this collective anger into a “will” that transcends biology.
From a creative perspective, it doesn’t make much sense, but fiction does entreat us to suspend our disbelief. This theory is akin to horror icon Sadako from The Ring, whose psychic power and death led to the creation of a virus-like cursed tape that aimed to decimate humanity. When compared side-by-side, it offers a pretty sensible outcome: the fallen samurai are Sadako, the mysterious larva is the killing will, and Kafka is the cursed video tape that will decimate kaiju-kind.
But that doesn’t say that this theory doesn’t have any glaring holes–it in fact does. Did another group of humans in the beginning of time fall into a chasm, and through their collective despair, create a daikaiju or honju that embodied their disdain for their fellow humans, leading to the proliferation of kaijus who seek to decimate the population? Why is Kafka the one person that the mysterious larva chose as its host and not Vice Captain Hoshina, whose ancestor did die during the Meireki era battle? Who knows. Alternatively, we could always assume this, though:
Aliens. It’s aliens. Why can’t it be aliens, anyway?
Like some of life’s mysteries, we can just say that the root cause of this kaiju invasion is the existence of extraterrestrial life. Matsumoto has barely given any lore towards the origin of kaiju, so the next best option to do is just attribute a species of aliens trying to take over the earth since the beginning of time as monstrous kaiju. The kaiju look alien anyway, and out of all the canon information we have available, this non-canon theory makes the most sense since it’s been done before (take another series titled Parasyte, for example). As that one History Channel “historian” did say once, “I’m not saying it was the aliens… but it was the aliens.”
