This is a great little image that really sums up the different sort of nudity fetish content you can find in NSFW art and fiction in a very neat way. As someone who writes fiction where nudity and nudity fetish content is the main theme, I find it extremely relevant to what I do, and I'm grateful to @Neku_ZX (Patreon) for creating and sharing it on Twitter.
I thought it might be fun to go through each of these in turn and talk a little bit about what I understand them to mean, and how I use some or all of them in my various novels and short stories.
ENF
ENF stands for 'Embarrassed Naked (or Nude) Female'. In its most basic form, it's a character caught or exposed naked by one or more other people, who are not naked themselves. The character doesn't want to be seen naked by others, even if they are happy being naked when they are not seen, and they experience embarrassment as a result. They would usually try to find some way to cover their nudity (if they can, they may not be able to) or get out of that situation (but, again, they may not be able to).
In some ENF the experience is humiliating or degrading for the character, while in others it is more humorous. Also, some erotic ENF adds to the embarrassment by having the character find, much against their will, that the experience of being seen naked causes them to become sexually aroused.
ENF is one of my favourite tropes in NSFW visual art, which is good because it's a popular one in nudity fetish art. I really enjoy it in images and comics because it's great to see the naked character on display blushing and embarrassed. I've also read some really good ENF stories. But it isn't one I have touched on much myself so far. I've included a little bit of ENF content in some of my stories, and a few scenes in novels, but for the most part ENF isn't the focus of my writing.
That will somewhat change when I publish my next book, The Tribulations of Omega Girl, as ENF is much more the dominant theme there, with a superhero storyline.
Exhibitionism
In exhibitionist content, a character (I'm generally referring to female characters in all these because that's what I write and view, but you can do these with males too) is naked in front of other clothed characters, but unlike ENF, in these situations the character is naked because they want to be, because they enjoy being seen naked and likely even find it sexually exciting to show their body to others.
The observing characters are not casually accepting of the naked character's nudity, they may well be shocked or offended - but equally they may enjoy seeing the character naked, often on a sexual level, although how much they make the naked character aware of this depends on the situation and writer/artist. It's certainly understood that both negative and positive reactions are equally enjoyed by the naked person.
I use exhibitionism a lot in my writing, and exhibitionist characters are really at the heart of the fiction I decided to create. The very first successful erotic story I wrote was all about a female exhibitionist rigging a strip game so she could end up plausibly naked in public, and in almost every story I write there is some element of exhibitionism; a female character finding they enjoy being naked in front of clothed people and find it exciting and arousing. Queen of my exhibitionists would have to be Becky O'Neill from the Naked Girl books, though - she's very comfortable in her identity as an exhibitionist, and finds it very thrilling to be nude in public and seen by clothed people, to the point where she is always looking for new ways to get out of her clothes and be seen, and when she isn't doing it, she's fantasising about it.
Casual Nudity
If there is a casual nudity theme, then a character will be naked in front of other clothed people, either in public or in a more intimate setting, much as they would in an exhibitionist story. But the difference here is that the naked character is not doing it for the thrill - they are simply someone who finds nudity more comfortable or pleasant than being clothed, or may just not see nudity as being a taboo thing for them due to background, culture, or personal beliefs. There isn't necessarily a sexual element to the nudity for the character (although their confidence may mean the scenario can be sexy for the reader), or if there is it isn't the focus of their feelings.
The other difference with casual nudity is that the clothed people around the naked character are as casual about the person's nudity as the naked person themselves is. Unlike exhibitionism, where the nudity is presented as surprising, shocking or exciting to the witnesses, here the nudity is just matter-of-fact and accepted by the people around as completely normal for that character (even if it isn't a social norm).
I like casual nudity in stories because it affords a lot of scope for 'only one naked' scenarios that go on for a long time without being interrupted because the real world wouldn't allow a character to be naked for that long. I do think these sort of scenarios can still be sexy even without an element of either exhibitionism or embarrassment, because they allow you to depict a character who is very confident and comfortable about their body and doesn't feel shy about being seen naked by people who are not naked themselves. This is something I personally find to be a very attractive quality and so it often finds its way into my work.
I suppose the ultimate in casual nudity stories would be my Brave Nude World, in which some social changes mean that the main character and some of her friends are able to walk around naked in public without fear of reprisal, and do so for no other reason than that they have a personal preference for nudity. But you see it in many of my stories whenever a character is naked with an accepting clothed person in a non-sexual way.
Oblivious Nudity
Oblivious nudity would probably be best described as depicting an 'Emperor's (Empress's?) New Clothes' scenario where a character is naked in front of clothed people without knowing they are naked. Perhaps their clothing has been suddenly damaged or torn off, perhaps magic or hypnotism was involved, or perhaps they simply left their home in a hurry and forgot to get dressed. But at the moment of the scenario, they haven't yet realised they are naked.
The people around them, like in an exhibitionist scenario, might be surprised, shocked, offended, or excited and pleased to see them; but the naked person themselves remains either unaware of, or confused by the reactions.
In the end, this might end up as an ENF scenario, when the person realises they are naked. Or it might even turn into an exhibitionist scenario, if they figure "what the heck, I might as well enjoy this!"
I like these sort of scenarios because they get around the problem of the fact that most people (unless they are exhibitionists) would probably find it difficult to be naked in public or in front of a large number of clothed people for a long time. But if they don't know they are naked, they have no problem.
I don't think I've ever written an oblivious nudity scene in any of my work. Part of the reason for that is that a lot of what I write focusses on the feelings of the naked character about their nudity. If they aren't aware they are naked, there is nothing for them to feel except normal. So I think it works better in erotica from a visual point of view; such as in the French comedy film 'The Names of Love', in which there is a scene where the female character leaves her apartment and walks all the way to the Paris Metro station, and even boards the train, before she realises she has forgotten to put on clothes and is completely nude.
Naturism
In a naturist environment, nudity is the norm for everyone. There is no sexual element, it is just casual nudity for comfort, health, and social connection. Your main character is naked, but so is everyone else, so they are not treated as different for as long as they are in that place.
For some creators and readers, naturist scenarios can still be sexy, because our brains automatically sexualise nudity. So depicting a character 'going naturist' can still excite because it allows them to be depicted nude, and also to be depicted as confident and comfortable with nudity and their body, which as I have said is a very attractive quality.
But the act of naturism itself is defined as being about social nudity and not sexual nudity. That is why it can take place between people with no romantic connection, such as family groups, or platonic friends, or strangers.
Although I am someone who enjoys social naturism myself along with my partner and friends, I don't tend to use purely naturist scenarios in my fiction. There are exceptions, of course: Brave Nude World has a strong naturist theme running through it, with Rachel being first and foremost a naturist/nudist who spends time socially nude with like-minded friends with no sexual aspect to it whatsoever. And in the story titled What Was Found When Lost, the characters being at a naturist resort serves as an explanation of why the lead female is walking naked in the forest. Meanwhile, Becky in the Naked Girl books identifies as a naturist as well as an exhibitionist, although she rarely encounters other naturists in the storyline. And in Sophie, the cover story used for the title character's nudity is that she is a very enthusiastic naturist, and this leads to a bit of non-sexual social nudity between Sophie, Laura and their friends.
But I don't feel that naturism lends itself particularly well to the sort of fiction I write, because I do share the belief that to practise naturism is not a sexual act. As a writer who is depicting scenarios that I want readers to find sexy and exciting, I don't feel that showing naturism as it really is meets my goals. I am aware of specifically naturist fiction, that is, fiction written by, for, and about, naturists, but this doesn't appeal to me. There are limited plot lines I think one can conjure for such a theme, and none of them I find interesting. I can see why some naturists would want to read about people like them, or people discovering how great naturism is, but it's not my thing.
That said, I do think there is a great possibility in including naturist characters in fiction where their naturism is not the focus of the plot, or even the defining feature of their character. An example of this would be Minami in the Japanese manga, and live action comedy drama, Million Yen Women. She is depicted as a nudist, but it is not a major part of the whole story.
Unashamed Nudity
The last category on the list is one which shares some similarity to the others, but also some distinct differences. In an unashamed nudity scenario, a character is not an exhibitionist, but still has some preference for, or at least indifference towards, nudity. Most likely, also, they do not find nudity to be taboo or socially unacceptable. They may be a very committed naturist, or from a culture or background in which exposed breasts, buttocks and genitals are not treated as private, sexual, or obscene. So, they will go naked in public or in front of clothed people without shame or concern for how they appear.
However, in an unashamed nudity scenario, unlike a casual nudity one, the people around them do not share the character's attitudes and beliefs. The world around the character is still one which sexualises nudity and finds it socially unacceptable, so they react more like the witnesses in an exhibitionist, ENF or oblivious scenario; that is, surprised, shocked, or excited/aroused.
It is likely that the naked character does not understand these reactions, and it may set them at odds with the other people in the scene; they may be confused, or angered, by people taking issue with the fact they are naked. Or, they may simply not care what people think. They are aware they are naked, and that this makes them different to the people who are not - they just don't see that it matters.
Like a lot of the other scenarios on this list, unashamed nudity gives a chance to show how a character is confident and comfortable with their body, which is a way of making them attractive and sexy to the reader/viewer. It is also a way to have longer and more involved nude scenes, as the character would see no reason or need to put on clothes wherever they were. It also requires them to be placed in a situation where they are the only naked person, or at least where the majority of people are not naked, which is a fun juxtaposition.
I think I've used this sparingly in my work but I have definitely enjoyed making use of it from time to time. My short story Nikki's Naked Weekend leads up to the title character learning to be unashamed of her body to the point where she arrives for her dinner with her neighbour Tom in the nude (although this is also because she wants to sleep with him so it is not necessarily that there is no taboo). In Brave Nude World several supporting characters go nude even when those around them disapprove, although in the narrative they are at least supported by law and a cultural movement. But probably the biggest unashamed nudity story I have is Carla Takes Her Clothes Off, where the title character gradually gains more confidence and comfort with nudity, to the point that she goes naked in several public places without concern.