Captain Marvel grinned at his sister Mary when the lightning flash faded. “Bet I can get naked faster than you.”

“You’re on,” Mary said.

Captain Marvel jumped out of his sister’s bed and stripped out of his cape, boots, pants, and tunic as fast as he could. He had a little trouble getting out of his underpants because of the erection he already had, but with the speed of Mercury he didn’t think it slowed him down that much.

“What took you so long?” Mary chuckled, hovering naked above the bed when he turned around.

“How did you change so quick?” Cap asked, shaking his head in disbelief.

“I’m just as fast as you,” Mary pointed out, “but I skipped a step. Instead of getting out of bed I just hovered above it and stripped out of my costume.”

“You got me there, sis,” Cap said as he stretched out on her bed.

“Here, Cap,” tossing something on to his bare chest. Billy picked up the scrap of cloth and recognized the panties that Mary wore under her costume skirt. “You seemed to be a bit upset when you realized that I gave Freddy a pair, so I thought you’d like one of your own.”

“Thank’s Mary,” Cap said, giving the panties a quick sniff. Mary hadn’t worn them for more than a few seconds but he could still smell her scent in the crotch.

“I’ll give you a pair of my regular panties too, if you want.”

“Clean or worn?” Cap asked, sliding out of the bed to look for his jeans so he could stuff the panties in one of his pockets.

“I can give you a clean pair right now,” Mary offered, “but if you want a worn pair you’ll have to wait a couple days.”

“I can wait,” Cap decided, “at least I can wait for the panties, your pussy is another matter.”

“Well get back here, then, because I can’t wait for your cock,” Mary said, sitting up above her bed. As Mary sat up her breasts quivered enticingly, catching Caps undivided attention. “Unless you have another idea.”

“I think I do,” Captain Marvel said with a grin. “You know how your tits are bigger as Mary Marvel than they are as Mary Batson.”

“Sure I do,” Mary said, juggling her tits in her hands. “I gain several years when I turn into Mary Marvel and it shows in my breasts as well as other areas. Just like you’ve always turned into an adult as Captain Marvel, even when you were only ten you changed into an adult when you used your magic word.”

“That’s true,” Cap said with a shrug. “But I was wondering, have you ever heard of a tit fuck?”

“Why yes I have,” Mary said, juggling her tits even harder than before. “And now that you mention it my tits are a good size for a tit fuck when I’m Mary Marvel instead of Mary Batson. So, is that what you want, a tit fuck?”

“Yes, that is what I’d like to try,” Cap said without taking his eyes off his sister’s breasts. “But how do you know what a tit fuck is? I know because Freddy’s been supplying me with porn for the last couple years, but how do you know?”

“Well,” Mary said slowly, “Freddy’s been supplying you with porn, but I’ve been supplying myself. About once a month I fly to New York, change into street clothes, and walk into my favorite sex store. I’m a regular customer now so they don’t even try to card me now, but even the first time I went there they didn’t bother to check my ID, and the few times they did bother I said I forgot it and they decided I looked old enough to be trusted. I wouldn’t be surprised if I have a larger porn collection than you and Freddy do.”

“Why didn’t I come up with that idea?” Cap mussed.

“Because you didn’t have to,” Mary pointed out, “you had your best friend Freddy ready and willing to supply you with all the porn you wanted.”

“Good point,” Cap sighed. “So what about it, Mary? Want to try a tit fuck?”

“Eventually I want to try everything that I’ve read and watched, so a tit fuck sounds good to me. So come up her and let me wrap these babies around that big cock of yours.” Mary stopped juggling her tits and pulled them open to give Cap a place for his cock.

“That does look inviting,” Cap said, hovering closer to Mary.

“Hold on a second Cap,” Mary said, letting go of her tits and reaching out to stroke her brother’s muscular arm and chest. “I can see why some girls would want to get into your pants with a physic like this, not to mention your good looks, or your cock. What is it, about 8 inches long and 2 inches in diameter.”

“I’d say that’s about right,” Cap said as his cheeks blazed red.

“So, not exactly porn star proportions, but a real pussy pleaser, right?”

“I’m not sure,” Cap admitted. “I didn’t think it would be a good idea to try fucking a girl as Captain Marvel, with my strength and speed it could be dangerous for her.”

“But not for me,” Mary said with a broad grin, “I have the strength and speed to keep up with you and enjoy every second of the fuck.”

“That’s what I’m counting on,” Cap agreed.

“You know, Cap,” Mary said thoughtfully, “if this is what you’re going to look like when you – that is Billy – grows up, you’re going to have to beat the girls off with a stick.”

“Well I’m not going to beat off all the girls,” Cap said, giving Mary a kiss that made her toes curl and her pussy twitch. Now that she was done examining Cap’s body he rose up, sliding his cock along her belly and chest until the tip poked through Mary’s tits and she pushed her breasts together to trap his prick. Mary slid her tits up and down Cap’s cock, licking the tip whenever it poked out from between her breasts.

“Yum,” Mary muttered, sliding her tongue along the head of Cap’s prick before it disappeared between her tit mounds again. “That is the tastiest cock I’ve ever tasted.”

“And just how many cocks have you tasted in your life?” Cap chuckled.

“Four,” Mary said, “that is if you consider Freddy, Junior, Billy, and you as separate guys.”

“Well, for only sucking four guys, you really know what you’re doing.”

“Thanks, Cap,” Mary said with a grin, “I’ve practiced on things like hot dogs and carrots, but today was the first chance I had to suck a real cock.”

“Well for your fourth cock, you’re doing a great job, maybe too good, I’m going to cum on your tits if you don’t stop now.”

“Well we can’t have that,” Mary said, releasing her tit’s and Cap’s cock at the same time. “At least we can’t have that until my panties start getting tight.”

“Right, cum in your pussy and nowhere else until you know you’re pregnant,” Cap said, pulling away from his sister and shifting around until he was between her thighs while they continued to hover above her bed. “Say, sis, why are we hovering above your bed anyway?”

“Two reasons,” Mary said while Cap rubbed his cock along her drooling slit. “If we start fucking full strength and speed on my bed we could leave it in splinters.”

“Good point,” Cap said, tweaking Mary’s erect nipples while he continued to slide his cock along her slit. “So, that’s the first reason for hovering above your bed, what’s the second.”

“Think about it, Cap, have you ever heard someone say they didn’t give a flying fuck about something?”

“Mary,” Caap groaned, “you really have to warn me before you come up with a stinker like that.”

“And what would be the fun in that?” Mary asked with a chuckle. “Now slide your pussy pleaser where it belongs. Fuck me, Cap, fuck me.”

“With pleasure,” Cap said, setting the head of his cock between Mary’s pussy lips and sliding forward with one fast hard thrust that buried his whole cock deep in his sister’s juicy cunt,”

“Oh, that is a pussy pleaser,” Mary purred, locking her legs behind Cap’s thighs while she pulled his face close for a kiss while he continued to massage her tits and the two of them rolled over and over above her bed.

For once Cap wasn’t worried about what would happen if he got so involved with fucking that he forgot his own strength. Just like Mary had pointed out, he could fuck her full strength and she’d give back as good as she got. In fact, right now her pussy was squeezing his cock so hard with every thrust that Cap had trouble pulling out of her pussy with every stroke.

Mary was enjoying the fuck just as much as Cap, her pussy had never felt so full or so hot in her life. Even so, every thrust made her wonder where she could get something even bigger to fill her fuck hole even more.

“Oh my God, Mary, you are such a hot fuck,” Cap groaned as he fucked his sister with enough force to make her body jump with every thrust while the two of them continued to roll around while the hovered over her bed.

“If I’m hot than you’re a volcano, Cap,” Mary gasped.

“You could be right, Mary,” Cap panted, “because I feel like I’m about to cum like a volcano.”

“Then slam your cock into my belly and hold it there so I can get a full load of your baby juice.”

“Whatever you want, Mary,” Cap said slamming his cock into Mary’s belly as hard as he could and holding up against his sister’s cervix as it spat cum directly into her hungry womb.

“Thank you, Billy,” Mary mumbled, burying her face into Cap’s muscular chest.

“No, thank you, Mary,” Cap said, giving Mary another pussy twitching kiss. He glanced at the clock on Mary’s night stand, “It looks like we have about fifteen minutes before Freddy gets back, what else do you want to do before the main event starts?”

“How about a quicky as only the Marvels can do it?” Mary suggested.

“With our speed a quicky could mean a full blown orgy from foreplay to cum shot in less than ten minutes,” Cap said with a broad grin.

“Five minutes would be better,” Mary said with a grin. “The way I look at it, now that I’m fucking I won’t be satisfied with one or two fucks a week – or as often as I manage to get them – I’m going to need a couple fucks a day. I figure if we can manage a full fuck session in five minutes I can find the spare time to fuck a couple times a day. All I have to do is leave home about 5 or 10 minutes early for school and part way to school I change into Mary Marvel and fly to your apartment where you change into Cap and we fuck like crazy in the five minutes we have. After we’re done I fly off to school and arrive in plenty of time to get to my first class. When school’s done I’ll take a few extra minutes to fly to Freddy’s Newsstand where he and I can take a few minutes to fuck between customers before I fly back home with no apparent time lost between school and home. And on the weekend we can all take our time to fuck at a normal pace so we have a chance to enjoy ourselves at a normal pace.”

“Sounds like you have things all planed out,” Cap chuckled. “And I for one like your plans, so why don’t we get in some super-speed fuck practice before Freddy gets here?”

No sooner did Cap finish speaking then he grabbed both of Mary’s tits and started massaging them at super speed. Mary barely had a chance to moan with pleasure when Cap started sucking on her erect nipples, turning Mary’s moan into a shriek of pleasure as he switched from one nipple to the other at super speed at the same time that he started finger fucking. Even as her body shivered through it’s first super-speed climax Mary managed to get her fingers around Cap’s hard cock and gave it a few strokes before Cap pushed his sister’s hands out of the way and pushed her legs open so he could reach her dripping pussy with one quick thrust.

“Fuck me, Cap, fuck me,” Mary screamed as the two of them tolled over and over while they hovered several inches above her bed. Mary slammed her way through another mind blowing orgasm and held her brother close to her body as her pussy muscles squeezed his cock with all her strength. Cap managed to shove his cock as deep as it could go in Mary’s tight pussy and he held it there as he came with a roar, firing another full load of cum in his sister’s belly.

“Oh wow, that was great,” Mary gasped when her body finished shuddering through one more orgasm. “So, how much time do we have before Freddy gets back?”

Cap glanced at the bedside clock and grinned before he said, “Looks like we have enough time for another super-speed fuck session. I guess that means we’ll have time to get in at least one fuck session every morning before school.”

“I think you’re right,” Mary agreed. “But for now why don’t we change back, I feel like a normal speed fuck session with Freddy for now.”

“That sounds good to me, too,” Cap said. “As much as I just enjoyed our super-speed fuck I’d like to take the time for a regular fuck.”

“You better hold onto my panties while I change to make sure they don’t disappear with the rest of my costume.”

“Good idea,” Cap said, picking his jeans up from the floor and pulling Mary’s panties out of the pocket before his sister said her magic word. After the flash of lightning Mary Marvel was gone and the much younger looking Mary Batson stood in her place with her brother’s cum slowly sliding out of her pussy and down her naked thighs. Mary Marvel’s costume had vanished along with her, all but the panties Cap still held in his hands.

“Here, Mary, hold on to these while I change, they shouldn’t disappear along with my costume, but why take any chances.” While Mary held on to the damp panties Cap called out his magic word and vanished in his own lightning flash, replaced by a naked Billy Batson.

The twins turned toward the back of the house when they both heard another crash of thunder. “Perfect timing,” Billy grinned, “there’s Freddy now.”