Magical heroine's best friend/second in command who gets brainwashed/mindcontrolled by the evil demons they fight, and has her body reconfigured by their vile magic.
The heroine tries to talk to her, to get her to snap out of their enchantment, but it's too strong. She assumes that they must be torturing her, making her experience hell inside her own mind/body as it fights like a puppet.
The demons reveal that in fact the better she fights and the more commands she fulfils for her new mistress, the more pleasure floods her body, which they've reconfigured to need a much higher level of pleasurable stimulation in order to function. They've been very careful to make sure she's always seeking out more ways to feel good, to have others provide the cocktail of delicious chemicals she needs to function. Especially since they made sure she wouldn't be able to get that pleasure on her own.
Stopping her from the constant orgasmic rush of their benevolence could kill her from the shock to her system, now.
So, of course, the heroine should surrender, should let her friend pin her down and rip the magic out of her to gift to the dark queen, and join her in servitude.
But the heroine can't accept that-- not after leaping back out of range, panting and breathless, and watches her friend spin around to drop to her knees. Not while she could hear the lewd, wet sounds of her friend's throat being used... Surely it's a lie, or surely there's some way to break the spell...
So she ends up managing to kidnap her friend, steal her back to their magical fortress to try and break the magic binding her, heal her of the demonic influence.
It's only when her friend's heart starts failing and she screams in agony that the magical heroine swallows her morals and shyness and pins her friend's hips down long enough to start fingering her and rubbing her clit.
The demons told her, after all, that her friend's body needed pleasure to function now... She didn't see any reason why it had to be from whatever perverted magic they used.
Her friend's screams turn to moans, for a time, but the relief doesn't last-- isn't enough.
The heroine hasn't done this before, not with another girl, only fumbled around in her own bed in the dead of night, but she's... read things. Seen things online.
She's surprised by how good it feels to grope her friend's chest, the heavy swell of her chest so much more than her own meagre handfuls, and the way her friend's nipple throbs against her tongue as she takes it into her mouth and sucks sends a shiver down her spine.
It doesn't hurt that, with her other hand still three-fingers deep in her friend's dripping pussy, she can feel how she squirts from that stimulation.
When she hears her closest companion breathily gasp her name, the heroine feels herself cum in turn, surprised at the intensity of the feeling that followed that simple call, one she'd heard so many other times. Between laughs while they were joking around off-duty, yelled in warning during a battle, exasperated when she was found exhausting herself after taking on too many responsibilities...
Well, this was one more that she would have to take up. And no one would stop her this time.
It takes time and some hastily ordered toys before they can get to anything approaching normalcy...
Multiple egg vibrators stuffed inside her holes, and a remote controlled vibrating piercing through her clit combine with a rotating cast of nipple suckers, piercings, breast pumps, weights, and clamps.
And, of course, dildos, and strap on harnesses, and a plug-in wand when they were in bed.
They were considering the logistics of how to install some kind of fucking machine.
While her friend-- girlfriend? it was still kind of unclear where those boundaries lay-- did regain most of her mind, her memories, her control... no matter what cleansing magic they tried, she still needed near-constant pleasure.
And her time among the demon hordes meant it was still so natural for her to just start begging for it, or humping things, or dropping to her knees to have someone (anyone) use her. Beyond the embarrassment, the disgusted or pitying or incredulous looks of people who encountered them before she could get them both away somewhere quiet to take care of things herself... it was becoming more and more tempting to just give in.
Let her friend get used-- she was literally asking people for it, after all.
Or the way sometimes she found herself turning down the strength of the vibrators just a little, and then later a little more, until she could see her friend's growing desperation, and it fuelled a growing, sadistic little ball of heat inside her.
When there was a giant monster attack just outside the city centre, she knew she couldn't be distracted during the fight, so she chanced it by stopping by one of the shadier adult stores they'd visited while out of uniform. It didn't take much convincing for the manager to help her install her friend at one of the gloryholes-- this one big enough to fit her friend's ass through, with her bent over a cushioned bench-- and post to the various online groups and forums and email chains they were part of that there was a free use slut available for all.
It probably should have made her pause to see the manager taking her cock out and stroking it before slipping inside her friend's pussy to start mercilessly fucking her, but there was no more time, she had to go handle the monster.
By the time she finished the fight (a faster victory than she normally managed, a feral sort of violence taking hold throughout), she was jittery and pent up.
Her magical wings carried her back to the adult store on gleaming contrails of light, and she didn't care who saw as she shoved the door open roughly and pushed her way through the line that waited for their chance at the captive slut in the next room.
The heroine would almost (but not quite) cum on the spot, seeing her closest companion reduced to such a cheap toy, mindlessly seeking pleasure from who or whatever would give it to her, by whatever means necessary.
Gone was the disgust and fear and trepidation when she'd first found out what had happened to her best friend so many months ago, now all she could think was that it was her turn to use her toy.
Whatever subconscious desires or prowess of control managed to transform her wand into a magical strap-on weren't pondered, though she appreciated the end result, and especially with how thick the thing was.
She almost managed to feel bad as she stretched her friend's well-fucked cunt out even more as she started railing her-- her friend's cries were muffled by the pussy she was currently being smothered by on the other side of the partition.
Later, she might have some sort of thought about the videos spreading across the web showing the foremost magical guardian of the area brutally fucking her former second-in-command in a dingy sex shop, other perverts pleasuring themselves and each other as they watched, or cautiously swapped out using her mouth, but at the time all she could think was yes, finally, mine.
When she pulled out, finally spent, the others there thought that would be it, that the fun show would be over, but instead the remaining spectators were told to go ahead and use her, until everyone was done.
And, well, if they had to slide a toy in alongside someone's cock, or two people used her at once, the moans of the person they were fucking never seemed diminished beyond whatever was filling their mouth...
The heroine would, eventually, discover that the source of growing headaches (that only lessened from fucking her slut toy) came from a pair of demonic horns pushing through her scalp... And she would think, and grieve, for a few moments, how things had changed... but when her next magical transformation came with a change in attire both darker and less modest, and her powers shifted to reflect her new nature, well. She couldn't find it in herself to care any more.
When tales of a new trio of magical guardians reached her, she wondered how long it would take to break them all in to join the demon queen's expanding harem...
