Tentacle Monster

The Tentacle Monster is a category of liminal species that is defined by their highly aggressive sexual appetite and their possession and use of tentacle appendages. While exceptions do exists, tentacle monster species are largely considered apex predators, are sexually predatory, come in incredibly diverse and versatile forms and are alien in physical appearance to the typical humanoid form.

Tentacle monsters are infamous and greatly feared for their ability to use sex and a creature's biological base instincts for sex against their prey. Even apex predatory species like Arachne and Devils can become prey to tentacle monsters and so most liminal beings actively fear and avoid interactions with the species. Some tentacle monsters can even prey on ghosts and spirits (beings that are normally immune to biological predation) and possess specialized appendages capable of interacting with spiritual energy, ectoplasm and mana.

Typically tentacle monsters use their tentacle limbs to ensnare and restrain their prey. They are masters of waiting for prey to come within reach of their tentacles or luring their prey to them by either hiding or presenting a benevolent/harmless facade until their unassuming prey is within reach. Once their prey is ensnared, the tentacle monster will then proceed to use their limbs to restrain the prey and begin assailing their body; seeking out, probing and penetrating inside the orifices of the prey's body for varying intents and purposes. Penetration is usually non-consensual and involuntary for the prey (although some "prey" do seek out interactions with these species of their own violation and encourage the penetration of their orifices with full consent), however, in frequent incidents, the prey's initially non-consensual attitude changes into active consent as the tentacle monster either breaks the prey's mental cognition or uses its knowledge of the prey's erogenous zones to manipulate their libido and sexual instincts into desiring continued sexual activity with them. If unchecked, this results in the prey succumbing completely to the tentacle monster and they ignore their instincts for self preservation by allowing and actively encouraging the tentacle monster to assail their body until their death or until the monster is otherwise done with them. This is why the tentacle monster is considered one of the most feared sexual predators amongst liminal species but also one of the most desired and idolised sexual partners amongst sex enthusiasts as even non-sentient tentacle monsters demonstrate a heredic knowledge and ability for carnal sex that rivals even the Devil species.

Note, that aside from a non-canon incident where Kimihito was transformed into one by a potion, there is no evidence tentacle monsters as described here actually exist in the Daily Life With a Monster Girl world. The closest thing would be the giant anemones Octo kept in her cave, but they were decidedly not interested in sex nor did they penetrate their targets, instead merely paralyzing and feeling them up.

Physiological Attributes

 * A tentacle is basically a flexible mass of muscle and as such can impart a lot of force. When used for combat tentacles can be used to grip and throw objects at people or wrap around and strangle them. Strong tentacles can even be used to impale people or crush them. They may also be used as (somewhat oversized) whips or bludgeoning weapons.
 * If not for the purpose of breeding, one of the reasons why Tentacle Monsters have sex with their prey may be due to the process of being incited to orgasm typically tires a prey out and so the monster takes advantage of this by continually inciting the prey's body into orgasming until it becomes too tired and weak to fight, which allows the monster an easier time to eat them, feed from them, mate with them, or otherwise enact their will upon them. Being penetrated and brought to orgasm also distracts the prey from what the monster is otherwise doing to them; such as binding their bodies, devesting them of their equipment, dragging them into their lair or to an orifice to be eaten. Sometimes the prey is so distracted by the pleasure that they fail to notice the monster penetrating deeper and deeper into their bodies until the penetrating tentacle erupts out of their bodies at the opposite end from where it was penetrating into. Additionally, large amounts of pleasure sustained for large periods of time may "break" the prey's mental cognitivity, rendering them completely docile or allow the monster (particularly those with psychic abilities) to access and feed on or warp their minds into being compliant and open to the monster's will. Entities that eat spiritual energy and souls also feed through this method as biological bodies emit large amounts of energy during the mating process and a body's soul can be temporarily open and exposed during orgasm.
 * For some other tentacle monsters the penetration of their prey's orifices may not be for the purposes of a sexual act at all but is simply a means to gain access to and feed on substances held within the prey's body such as sperm, ovum/eggs, milk, urine, feces, or chemicals and endorphins emitted by the brain (predominantly accessed via the ears but can also be accessed via the mouth, nose and/or eyes). Some monsters even desire to gain access to the contents of a prey's stomach and will do so by penetrating the mouth, anus or navel.
 * Other reasons for penetrating their prey's orifices may include as a simple means to gain a better grip of their prey and render them immobile, or a means to enter their prey's body for physical amalgamation or to gain access to an internal organ, body part, or their soul for acquirement or for feeding.
 * Penetrating orifices may also be a method to kill their prey; either via asphyxiation (by inserting a tentacle down the victim's throat to block the air passage), internal impalement (inserting a tentacle into the navel, urethra, vagina or anus and continually penetrating into the body, rupturing any organs along the way, until it exits out via the mouth, or in through the mouth and out via the vagina or anus), precise impalement (such as penetrating the ear or nose canal to impale the brain or penetrating the vaginal canal or navel to gain access to and impale the heart hidden within the rib cage) or in preparation to rend the prey's body apart by inserting as many tentacles in as many orifices as possible and then continually pulling outward in opposing directions until the prey's flesh exceeds its capacity to stretch and tears away from its skeletal structure. To a similar end a tentacle monster can also penetrate a prey's orifice with a tentacle too large (or increase the girth of a tentacle the prey has already been penetrate with until it is too large) to naturally fit the prey's body, forcing the prey's body and flesh to tear around it as the monster continues inserting the tentacle inside them.
 * Yet another option a tentacle monster can use to kill their prey is to use their penetrating tentacles to inject the prey with hazardous substances (eg. acidic sperm, digestive acid) or hazardous amounts of substances (amounts that cause the prey to drown or their body to exceed it's physical constraints and burst). Sometimes these substances incidentally act as the monster's sperm or ejaculate but the prey is physically incapable of handling the substance injected within them (due to cross-species incompatibility) and they die from the experience.

Genre History
The tentacle monster's prominence in Japanese erotic literature largely arose due to influence from the aesthetics of censorship in western civilisation.

One of the earliest examples of Tentacle Monster erotica is a shunga illustration (erotic artwork that was commonly accepted as non-taboo in Japanese life) from the 1814 novel Kinoe no komatsu; popularly known as  where a Japanese pearl diver is depicted being captured, enveloped and forced into receiving cunnilingus from one octopi as another gropes and kisses her. While western audiences often interpret Hokusai's illustration as rape, Japanese audiences view it as consensual, particularly as the dialogue in the illustration shows both the diver and the two octopi expressing their enjoyment with the situation; with the large octopus exclaiming its delight in finally ensnaring her, complimenting how "ripe and full" her "bobo" is and expressing his desire to drag her beneath the ocean to the Dragon Palace to envelop her, while the diver herself exclaims how pleasurable being sucked by the octopus is and encourages the octopi to touch her and continue "sucking at the mouth of her womb" as she orgasms. The Dream of the Fisherman's Wife is not the only work of Edo-period art to depict erotic relations between a woman and an octopus. Some early carvings show cephalopods fondling nude women.

In the late 19th century (1882) Joshua Handley, an English artist and photographer for erotic literature in Paris, traveled to Japan to document the less well-known aspects of the Japanese and their culture. This resulted in him viewing the Dream of the Fisherman's Wife and forming an obsession with cephalopod erotica. Handley attempted multiple times to publish illustrations similar to Dream of the Fisherman's Wife in England, even coming up with some of his own involving female pearl divers, shipwrecked gentlewomen or unwary bathers who would fall prey to an octopus and become enmeshed in its tentacles, however, his publisher was appalled by the content. Not by the tentacles and rape (which they believed would appeal to people with "darker sensibilities") but at the notion that the women in the stories actually enjoyed themselves as they succumbed to tentacles and suckers. Handley eventually gave up trying to produce his artworks and, ashamed of his tastes, abandoned all involvement with pornography and turned to illustrating children's books under his mother's maiden name.

As part of the Meiji Restoration (1868-1912), which saw Japan adopt many aspects of western civilisation in order to "become more civilised", Japan adopted new laws influence by Victorian-era Europe to forbid public nudity (where previously Japanese men and women were free to walk around topless or in loin-cloths should they wish) and multi-gender public baths. During this era, creation of traditional Shunga art was also restricted.

Restrictions increased further during the years surrounding World War II, forbidding all erotic art and literature, until post-WWII when the occupying Allied Forces imposed a number of reforms on the Japanese government; which included a lessening on restrictions of erotic expression. Due to this, while “obscenity” (which included depictions of exposed genitalia) was still illegal to portray without censorship (which led to the creation of the "Black Bar" and "Mosaic Blur" to censor the offending material), the diversity of sexual acts that were now permissible to use led to a rise in erotic fiction.

By 1990, in their pursuit to create new material, erotic artists had devoted their efforts in creating new ways to either circumvent the "obscenity law" or to otherwise eroticize otherwise banal subjects, however, it was artist Toshio Maeda who is credited with coming upon the notion that, while the law forbid depicting traditional human genital-to-genital intercourse, it did not forbid depicting pseudo-genital-to-genital intercourse. Following this revelation, Maeda creates a new erotic manga that depicts women in sexual situations with non-human creatures who use tentacle-appendages to penetrate and otherwise assail the female characters. As the monsters did not have a defined gender and did not have/use human genitals (as they are strictly defined by the law), the sexual acts could be shown uncensored. Furthermore, the diverse sexual utility that these fictional creatures brought to the conceptual table meant that numerous fetishes could be believably implemented at the same time.

The earliest animated form of tentacle assault was in the 1985 hentai OVA, though the scene in question was removed when the OVA was re-released in a non-hentai form. The first non-hentai anime production portraying tentacle assault was the 1986 anime OVA, which featured a female Chronos soldier named Valcuria being enveloped by the 2nd biological Guyver suit when the suit produced tentacles to fuse with her, finding and penetrating all of her orifices in the process.

Toshio Maeda produced 1986's, which popularized the trope of tentacle rape and featured a scene where a nurse gets torn apart by the tentacles assailing her which grew to serve as the template for tentacle rape scenes. In 1989, Toshio Maeda's manga Demon Beast Invasion created what might be called the modern Japanese paradigm of tentacle porn, in which the elements of sexual assault are emphasized. Maeda would go on to create 1992's and 1995's, both of which are additionally considered staples in the Tentacle rape genre.

The use of tentacles in live-action films started in American B-movie horror films and has since migrated back to Japan. Producer Roger Corman used the concept of tentacle rape in a brief scene in his 1970 film and he would again use tentacle rape while producing  in 1980. The scene was so graphic that the film's director, B. D. Clark, refused to helm it and the actress whose character would become the victim refused to do the full nudity required, so Corman directed the scene himself and used a body double for some of the more graphic shots.

Trivia

 * The tentacle monster is a source of great amusement for the anime/manga fandom, is often brought up in a joking manner and is subject to much parody from inside and outside the anime community. Unfortunately, it is also used by those outside of the fandom to exemplify anime and manga (and those that enjoy them) as being a perverse and inappropriate medium.
 * For some, the fetish of seeing men and women being subjugated, exposed and bred/mated by something that is not human appeals due to the nature of some cultures considering animals to be sexually superior to humans. These cultures view the fact that because animals conceive more easily than humans, give birth faster/more easily, have more offspring per pregnancy, and possess attributes that allow them to survive, fornicate and flourish naturally in their habitat (without assistance from tools), leads to the belief that animals (and by association, non-humans) are superior to humans on a primal and sexual level. Due to these beliefs ancient cultures have attempted to copy and emulate animals and animal-attributes for centuries. Due to these ancient beliefs, the notion of a human engaging a non-human in sex (be it an animal, beast, non-human or alien) arouses the natural instincts within them and dictates a desire to mate with a superior being to, objectively, produce stronger offspring.
 * Influenced by the notion of their superiority, people wanting to experience sexuality on a deeper, wilder level are aroused by the tentacle monster's combination of inhuman grace and power, their inhuman wildness, and their exoticism. "It's the physicality of tentacles, soft, flexible, fully controlled, and the multiple uses for suckers are mind-boggling. Mixed with restraint fantasy and the idea of being totally immersed in the sex. The tentacles are arms, that caress but they're also covered with suckers. Flexible arms that caress, grab, hold and penetrate, covered with countless pseudo-mouths to suck and kiss - it's a powerful sexual image. Some do not like the rape fantasies but I love the idea of having so many arms and mouths and hands all over my limbs and body, doing things to me that no human can."
 * No doubt possessing a domination-submission component, the fetish also runs parallel to group sex fantasies, which are driven by the instinctual desire to be wanted and desired by multiple partners and be mated by as many appendages as possible (which objectively results in the mixture of a wider/stronger gene-pool within the resulting offspring). Women who enjoy the fetish of tentacle sex have admitted that they imagine it would be quite stimulating to have all of the orifices of their body (vagina, mouth, anus, urethra, navel, nipples, nose, ears) exposed and pleasured at once, while still also having the rest of their body being continually held and caressed while doing so (a task that a single human partner can not achieve). Additionally, as their partners are animals/non-human, the women would not be unconsciously comparing themselves to them during the sex; worrying if their body is visually or olfactorily appealing, or whether the animal is going to call them in the morning; habits that they often experience when engaging with a human partner and often result in a woman losing her arousal/enthusiasm in the sex.
 * Some also enjoy the rape aspect of of the fetish, of being overpoweringly desired and taken/bred/violated by the tentacle monster without the nuance of achieving their consent. They are aroused by the notion of being so physically dominated/out-classed/overpowered by the superior entity that they are in no way in control of what happens to them or their body to be taken advantage of on a primal/instinctual scale, possibly impregnated or even eaten/devoured. This arousal towards fantasy scenarios that they may find undesirable and fear occuring in reality is a neurological process that humans develop to help cope with them. For example, a girl who stresses over gaining total control of themselves and their environment to succeed may, as they grow older, develop an arousal towards the fantasy of having that control being rendered ineffective (eg against a non-human) and being reduced to the helpless animal that they believe themselves to be. While this view of themselves (as a helpless animal) may be a source of psychological grief and stress, as it is viewed and examined as part of their sexuality the emotional stimulation that the scenario produces helps to stimulate their labido, which is a more positive emotion than their grief (which would occur if the scenario was viewed with sadness), their paranoia (which would occur if the scenario was viewed with fear), or their rage (which would occur if the scenario was viewed with anger) and as a result the woman can handle the burden of this fearful scenario of themselves better and more healthier than if they viewed it from a negative emotion. Additionally, through the fetish, the woman may be able to start losing their fear of having no control after examining how pleasured they became in the fantasy and may start incorporating the scenario into reality by transitioning it first through sexual play and then incorporating it into their daily routine. In closing the fetish acts as a neurological "self-help" mechanism developed by the brain to deal with stressful factors.