The Demographic Crisis of Monster Musume

By Edward Lamarck

Valentine’s

Day is celebrated primarily by those with a romantic partner. For the lonesome few left behind this season, some comfort can be found in the genre of harem anime, a staple of modern Japanese television. From High School DxD to the more infamous School Days, the tropes are generally the same: an average-looking young Japanese male suddenly finds himself at the center of a harem with beautiful (sometimes magical) women all vying for his attention. Comedy ensues, as well as copious amounts of ecchi fanservice.

My fellow otaku are already very familiar with these shows and accompanying manga series. Some are better than others, with an actual storyline taking precedence over the constant accidental groping or upskirting. Very often the female characters are rather interesting because of their different personalities and interests, not just their sexy attire or embodying a certain fetish the audience is likely to have. A handful of harem anime are great examples of creative worldbuilding with high stakes, such as Arifureta, while others are genuine tearjerkers, such as Clannad. There is something for everyone here, if you catch my drift.

Upon reexamining one particular harem anime that I am fond of, I discovered an unsettling plot element that raises many disturbing questions. For those who have seen Monster Musume, it’s an important detail that is quite easy to miss. The manga makes the situation even worse by tenfold. Allow me to explain in intricate detail what this franchise is before delving into the science behind Japan’s most notorious harem anime of the 2010s. I hope you will enjoy this educational experience as much as I did.

To give a basic rundown, Monster Musume (which translates to “Monster Girls”) is about the daily struggles of a college-aged Japanese man who lives in a world where oddly-attractive mythological creatures exist. Not only that, but the government of Japan is beholden to the Interspecies Cultural Exchange Act, which was designed to integrate/assimilate these creatures into human society. Our protagonist, named Kimihito Kurusu, is given the highly enviable task of choosing one of several monster girls to marry in order to prove that coexistence is possible. Really inspiring stuff!

However, living alongside these previously hidden species, referred to as “liminals,” brings forth many new challenges. Their unique anatomies and cultures often clash with modern human society, but in this strange collision between different peoples, love can blossom. In fact, it does so frequently. A new love interest is introduced in almost every episode of the anime. From centauresses to harpies to mermaids, there is no shortage of options for our intrepid hero to wed and bed. At the heart of this franchise stands the objectively best girl, Miia, a half-snake, half-human lamia.

Miia is the first liminal character introduced in the manga and anime. She lives with the protagonist thanks to a mix-up with her exchange program and falls head-over-tail for him because he is accepting of monsters. A minor plot point of the series deals with the prejudice that humans direct towards liminal species, and sometimes Miia herself is subjected to cruel treatment by humanity. She is by far the most dedicated member of Kimihito’s harem, striving to prove herself at every available opportunity against the competition.

Her obsessive drive to marry Kimihito may seem strange, and even deadly on a few occasions, but it makes perfect sense when learning about the complexity of lamia culture. Based on their traditional clothing style, which is inspired by costumes worn by Middle Eastern belly dancers, and the desert-like biome that lamia are shown to inhabit, it can be reasoned that Miia’s homeland is somewhere around the Mediterranean. Lamia in Greek mythology was also said to have been the queen of Libya, providing further evidence of Miia’s kind living in that region.

Geography aside, the fundamental problem that every lamia in Monster Musume has is their extreme libido. As an all-female race, they can only reproduce by acquiring a human male as a mate. Their traditional practice is to kidnap human males, forcibly mate with them in massive orgies, and brainwash them with aphrodisiacs so that they become a docile “communal husband.” Polygyny is the norm here, not the exception. Miia finds this practice abhorrent because it is devoid of both romance and consent, and she carefully protects Kimihito from others of her kind, including her own mother. It should be noted that Miia’s father escaped from the lamia village, being unable to tolerate life as a communal husband due to his fear of snakes. There is no simple comparison to make between lamia breeding methods and real-world biology. I am not aware of any species completely dependent on another to sexually reproduce. However, the gender dynamic between lamia and humans can be compared to African lions. The male-female ratio of lions can range from 2:1 to 3:1, with females always outnumbering males. Very, very few male cubs survive to adulthood. Genetic diversity is therefore limited among lion prides, where practically every female is related to each other. Combine this with overhunting by humans, it becomes clear why lions are endangered.

The lamia tribes in Monster Musume face the same dilemma. In chapters 27 & 60-63 of the manga, it is explained that the species is suffering from a population crisis. Too few men are available to satisfy the lamia’s need to reproduce, and the lack of genetic diversity increases the risk of inbreeding. The stipulations of the Interspecies Cultural Exchange Act also prohibit kidnapping human males. The true goal of Miia’s exchange program was to find suitable human mates for her tribe, though she reneged on this ambition in favor of a classical, monoga- mous relationship, as is right and proper.

According to the best character in the series, the normal gender ratio of lamia women to human men in the village is a shocking 100:1! Lamia who reside at the top of the social hierarchy, either due to age or occupation, have more immediate access to the communal husband than the rest, keeping population growth more stable. Additionally, it reduces the risk of inbreeding by preventing the husband from unknowingly mating with his own offspring. The human male has little to no role in child rearing, a trait shared with some avian species with female-leaning sex ratios, such as hummingbirds.

At the end of chapter 63, a compromise is suggested between the lamia traditionalists and the younger generation who wish to experience true romance. It involves sending out younger lamia women to find their own husbands across the globe, engaging in the international monster exchange program just as Miia did. A side character in the village posits that the new sex ratio between humans and lamia should be 5:1, or one husband for every five lamia. This is arguably the worst possible outcome for both species. Once again, we can look to actual science to explain the dire consequences of this decision.

It is stated that the child of a human male and a lamia will always be a lamia. No exceptions, no weird hybrids. By sending greater numbers of lamia out into the world to reproduce freely, rather than restrict their habitat to one area, it creates the conditions for the lamia population to explode and turn their kind into an invasive species. It likewise reduces the number of human males who can have offspring with human females, repeating the same demographic crisis on a larger scale. While the manga does not elaborate on what might happen in this situation, it goes to show that traditional cultural practices on marriage often have a valid purpose behind them. To clarify, if human men exclusively married lamia women for several generations, it would end with the mutual extinction of both species, because no more males would be born. Procreation would be rendered impossible.

This may not be such a big problem if lamia were not so sexually desirable. Even without their homebrew aphrodisiacs, these serpentine women are said to be irresistible on account of their intense sex drive (increased dramatically during full moons), large breasts, and natural charisma. Coitus with a lamia, according to the manga and anime, typically lasts several hours and requires intense preparation. Unlike human women, lamia are less choosy when it comes to male appearances or income (though these still matter considerably). Communal husbands are preferred to be either strong, handsome, or wealthy, but these are hardly prerequisites considering Kimihito is none of these. The main trait that is sought after is endurance in the bedroom and sexual prowess.

The mating habits of lamia must be compared with two other liminal kinds in Monster Musume to get a better grasp on the topic. For example, harpies are another mono-gendered species that require human males to produce offspring. However, they are migratory by nature and do not permanently settle in one habitat. This allows them to have brief flings with men around the globe rather than having lifelong partnerships, preserving genetic diversity while keeping a stable population simultaneously.

By contrast, centaurs throughout the series have wildly different strategies to reproduce. There are male and female centaurs, yet sexual selection over multiple generations has rendered male centaurs overly brutish and animalistic. The strongest males held exclusive access to females, giving rise to a warrior culture among the species. Human men were then considered to be more desirable by female centaurs, as they were more gentle and affectionate in comparison, yet they could only serve as “teasers” to provide foreplay while the male centaur inseminates the female. This reduces men to perpetual cuckoldry. Nevertheless, the preference for human men has also dealt a critical blow to the centaur population, as centauresses commonly reject their own males for sex altogether.

The story arc involving Miia’s village finds a different conclusion than the one I have described before. The lamia instead offer human sex tourists to enter their village, having their way with them as soon as they arrive off the bus. While this keeps their numbers partially under control, it raises their genetic diversity to a whole new level. It’s treated as a win-win scenario, though there is still an unspoken risk of overpopulation within the village.

This entire manic tirade of a harem manga and anime was created for the whole purpose of exploring a fan theory that I have had for many years. I call it Liminal Population Theory, and it encompasses everything that I have written above. Much of it is speculation backed with scant evidence from the source material and real science. If nothing that I have written has left an impact on you, appreciate the fact that the first volume of Monster Musume was #1 on the New York Times Bestseller list for two weeks straight upon publication, and subsequent volumes were always within the top ten. Lust for monster girls has clearly reached both sides of the Pacific, and for fans like me, it’s not hard to see why. Even the manga author was surprised to see his creation becoming so popular in the United States.

Not to mention, a life-sized dakimakura body pillow of Miia was released in 2015 that was 23-feet long, or about 7 meters. It was sold for the reasonable price of $805.

To leave you with a quote regarding manga author Okayado’s inspiration for Monster Musume, he said during an interview with the Anime Herald that “Cute girls were the first thing I had confidence in.” He has certainly used his artistic talent to share that confidence with others.