Spike arrived at Rarity's a bit early in the morning, before she would have any customers. Just because it was his birthday didn't give him any right to interfere with her work schedule. He was curious what her present to him could be that he had to come over to get it. He doubted she would be making him a dress, perhaps she had started working on male's attire as well, and planned to make him a suit.
When Rarity stepped into view, Spike realized that Rarity's birthday present to him didn't involve clothes. If anything, it involved a distinct lack of them, made evident by the stark naked unicorn sauntering over to him with a smile on her face that let him know she had intended his, and he hadn't just accidentally caught her on her way out of a changing room or something.
Spike knew full well that this wouldn't be a romantic meet up, as Rarity and he had had more than one talk about the subject and mutually decided that it wouldn't work, for more than just the obvious reasons. As Rarity stepped close to him though, he figured she had decided while romance was out of the equation for them, sexuality didn't have to be, which he could happily agree with.
Rarity's hands began to move over Spike's body, holding him closer to her body. She often forgot due to his short size that he'd stopped being a child quite some time ago. The incident with him building his own dragon horde had marked his maturity, and he was in fact fair game as far as sex and relationships went. Rarity often wished she could feel some romantic attraction to the dragon boy, as she'd felt guilty more than once for not being able to return his affections. At the very least, she supposed she could give him a little physical pleasure to make up for it.
Spike, having given up on his chances with Rarity as a mate quite some time ago, was visibly excited by this, a spot of dampness forming at his crotch as Rarity's hands slid under his clothes, feeling along his scales and moving down his body to his ass, giving it a firm squeeze that sent a small shudder up his spine. The white unicorn's hands then trailed across his hips to his pussy, tracing along the edges of it teasingly before rubbing against it gently.
"Rarity~" Spike groaned, his mind not functioning well enough under the teasing to think of anything else to say. Spike was actually making things worse for himself by doing so, as his desperate groans were simply adorable to Rarity, and she was tempted to keep going just to hear more of them. Luckily for him, the only thing his cuteness invited more than teasing, was fucking.
Rarity pulling his pants and underwear down, her levitation pulling off his shirt as she got to her knees behind him. She was already unreasonably stiff from the cunt boy's body, and Rarity found it remarkable that Twilight was able to keep her hands off him at any given time. Rarity had to force herself not to just ram in dry, alluring as the thought of it was. She was no heathen, and so took her time, working her tongue inside of Spike's warm, wet slit, tasting his odd, but nonetheless pleasing, favor.
While her tongue worked his pussy, her hands kneaded his ass, a single finger poking gently between his cheeks and brushing against his hole, threatening to push inside, but never doing so, leaving Spike in a state of anticipation and making him more sensitive to the work of her tongue inside of him. He groaned when her tongue pulled out, as he had just been close, but the thought of the greater pleasure that would follow kept him from complaining.
Rarity sat down, her cock sticking directly up into the air. Spike stood above her, kicking off the pants and underwear around his ankles so he was fully naked. Rarity's hands reached up to his hips and began lowering him down onto her rod. He moaned as he felt it pushing inside of him. Aside from Twilight, he'd never had anything but his own fingers inside, he'd never even tried dildos before. As he moved his hips down to take more inside, he found Rarity to be a bit bigger, length and thickness, than Twilight.
Rarity was groaning from the moment she entered the young dragon, his small form making him extremely tight around her cock, the tightest she had ever had in fact. Rarity happily told him so, the dragon gaining a bright blush across his face. That was a bit more than Rarity could handle. She pulled his hips down harder, grunting as she forced more of her cock into his wet, tight cunt. He yelped at her sudden depth inside of him and the feeling of his walls being stretched out, but couldn't deny that it felt intensely good.
They were still for a moment, both all but certain that any movement would make them cum. It was Spike who made the first move, beginning to slowly buck his hip against Rarity, making her cock move inside of him. The motion sent an initial jolt of pleasure through them that made it impossible for Rarity to stay still. She thrust up into him, and soon the dragon was riding her cock roughly, bouncing up and down on her length and bringing her closer to climax with each movement.
Spike came first, as well he would have given the circumstances, but the extra tightness brought on by his orgasm had Rarity going over the edge shortly after. Twilight had given him dozens of mouthfuls over the years, but very, very rarely ever finished inside of him. The feeling of the warms pumping into him caused him to cry out, another climax hitting him.
Rarity sighed in relief as her seed unloaded into the dragon. As they panted and attempted to recover, Spike dismounted Rarity's member. He made an effort to get to his feet, but quickly realized that wasn't happening until he caught his breath, and fell back to his fours. In this position, not only could Rarity see the cream pie she'd made of his pussy, but also his cute, tight, supposedly virgin ass.
Rarity wasn't sure what came over her in the moment, perhaps there was something chemical, some reaction of the pheromones let off by a dragon, that had driven her deeper into lust than she had expected, but she leaned forward, moving his tail out of the way, spreading his cute ass cheeks with her hands, and driving her tongue inside of the tight, puckered hole of Spike's ass.
Spike yelped in surprise as he felt her tongue enter his anus, his claws digging into the floor from the feeling. It didn't feel bad or painful, but much different to what he was used to. He didn't want to stop Rarity, at first purely because he didn't want her to feel embarrassed for anything, and then because her actions began to feel good as her tongue probed his tighter hole.
Rarity forced her tongue as deep inside as she could, lubricating his anal walls before withdrawing her tongue and moving forward, lining up her member to his ass, "Don't worry Spike, I'm sure it might hurt a bit at first, but it's bound to feel good after~" She purred to his as she held his hips, "It might seem too tight, but if it doesn't fit," She jerked her hips forward roughly, "We'll make it fit~"