So you want to write a chastity story? Perfect! Here is a little step-by-step on how to do it. Don't worry, it's easy! The majority of the stories all follow the same tried and true methods! Let's begin!
Step One: The before story flair. You can choose to include this or not. Basically, you made a statement beforehand stating it's a work of fiction and that if you don't like this kink don't read. Everyone will ignore this and will still proceed to read even if they dislike it.
Step Two: The Characters.
Characters are the easy part, you have your Main cast and you can have a few support characters. Don't worry about characterization or growth this is a website for porn we aren't here for that. Instead, insert paragraphs of Wattpad-like descriptions of your characters and what they wear at all times. ESPECIALLY the female characters.
Now a lot of stories follow along the POV of the one wearing the chastity device (Cock Cage or Belt depending on the wearer's genitalia)
If your character is a male, make sure he is completely stripped of all agency, he can't have any say in anything it doesn't matter what the dynamics of the relationship is (We'll get to proper BDSM dynamics later). If he does have a say, it's a non-choice or it's forced. Remember consent doesn't matter if you're a man. The male character no matter his physique or mental capacity is entirely trapped and unable to escape even the most basic of cock cages. (We'll discuss the merits of 'realism' in a fictitious story later)
Also, remember no matter the gender of your 'sub/slave' they are completely without support. They have no friends or family they can contact, and all services of combating abusive relationships ie (Police, International Domestic Violence Hotline, and other local programs) are completely ignored. They will at all times feel too 'embarrassed' or 'shamed' to ask for help no matter how much abuse they put up with. (This too will be covered in realism)
Now, remember your male sub/slave has no free will or choice in anything. The moment the cage goes on he's an immediate slave. He will do any and all things the 'Dom' or 'Mistress' tells him because he's just that desperate. He will immediately be perfectly fine with his long-time partner cheating and he will immediately cave and accept any and all sexual requests/demands. Never pay attention to his mental or physical health, just assume he can take it and go from there.
Now, for the female belt wearers. These are rare and not written about as much but there is still plenty of examples. You can apply everything from the male to the female belt wearer. She too will have no say or agency, will feel too meek or embarrassed to ask for help, and will do as asked. Her physical and mental health will constantly be taken for granted and she will have no support either.
No matter the gender just remember they are now objects not people.
Step Three: The Doms/Mistress/Mam's/Sir's Basically the person in charge of the relationship. Don't bother writing a backstory to them, don't bother giving them humanizing or redeeming qualities. They are entirely one-note and shallow. To put it shortly make them royal assholes that you just want to take a gun to the head. They are condescending, abusive, manipulative, gaslighting, and don't believe in 'Safewords' at a BDSM club these people would be banned for life but in fiction, they are praised and people 'wish' their dom could be like that.
The female version will always be hot and or sexy, and impossible to say no to. She will talk down or over her sub will convince the sub everything is entirely their idea and she's just 'being a good sport for going along with it' bonus points if she's the wife or girlfriend of the relationship that had been vanilla but after a month of being in charge, she decides she 'likes' this lifestyle too much and becomes the ultimate form of a dominating cunt.
It doesn't matter if she originally wasn't into any of this before but the moment she experiences the taste of power it immediately corrupts her. She will begin cheating and chucking her husband/boyfriend she will deny and tease to the extreme. Go back on promises or change her mind on a whim. She will demean and demoralize and be the exact opposite of a 'loving wife'.