The twins with an interesting secret

"I think I'll take that threesome."

"Alright. Fuka! Futaba! He's ready for you now!"

Out from the lower deck came identical girls, save for how they were dressed and wore their hair. Both were five feet tall brunettes with C cups.

"I'm Fuka and this is Futaba. Excuse any shyness she may have. It took her a while just to open up to the rest of the crew, but hopefully her sexual desire overrides all that."

Fuka wore a strapless dress that stopped mid thigh and started just above her areolas. She had antenna hair and a ponytail. Futaba on the other hand wore a long sleeved midriff with a cleavage window, and a long frilly skirt. Her straight hair was long in the back, cheek length on the sides, and even bangs in the front, a hime cut in other words.

"Since our little Futaba's probably nervous enough as it is, we'll excuse her of the pressure of an audience. We'll make ourselves busy."

Futaba's eyes darted around, then when it was just the three of us, her expression changed dramatically, looking at me with lust as she hooked her fingers in her cleavage window to fully expose them.

"Alright stud, I've waited a long time to find a good looking man to deflower me. Every day I masturbated to my crewmates, holding back from settling for one of them as my first, but now my first experience will be penetration with this."

She kissed me and started jerking me off. Fuka helped her pull down her skirt. She wasn't wearing any underwear and her clit was..visibly throbbing, which seemed weird but that wasn't the half of it.

"She's so serious about this that she's going to show you something she's only ever shared with me. Please except her feelings."

"You see, I ate a certain fruit, looked like an eggplant but with swirls and a nasty taste. Ever since, I got a unique body I've been ashamed of, until for some reason I stopped feeling that shame."

Her clit grew rapidly and changed shape. Covered in a lubricating fluid, it became a fully functioning penis rivaling my own.

"The Futa-Futa fruit made it so my clitoris becomes a dick if I'm aroused enough. Shame or no, I worry the crew wouldn't see me as truly female anymore if they saw this. Or what if they want to use me as their sexual plaything. I know it can be offputting, but I have a perfectly good pussy right under it, so if you would just ignore it and have normal sex with me I would be so happy."

She positioned herself for doggy style, holding her dick between her thighs to keep most of it out of sight from my angle. I was already using my imagination on how to maximize the potential of this unique situation.

"Fuka, while I'm fucking your sister, you jerk her off. Sound good to you?"

"I never thought of that before. She is my sister, but I don't feel like that's a problem."

"When I had shame about this, I thought about it but felt like having my sister cross that line was the last thing I would do. Now, I don't see a problem either."

You liked where this was going, and as you got the tip in, Fuka starting stroking her sister's clit-dick with both hands, each hand separately focused on the shaft and the tip. When I went balls deep and started moving, her dick grew more, up to a foot long.

"It gets longer the more aroused I am, so I guess this is my max length. I don't know how much longer I can hold back from cumming with all this stimulation."

"Go ahead and cum sis. I'll catch it."

I felt her orgasm through her insides. To Futaba's surprise, Fuka used her mouth to prevent any spilling. Based on her frequent swallowing, it must have been a large load coming out quickly.

"That was the hardest I ever came. Oh Fuka! You're still sucking it?! Fuck, fuck, fuck that feels good!"

"How about Fuka gets underneath to be fucked by you in missionary?"

"Full on ****? Okay, I'll do it."

"But she's a virgin too. Don't you want to be the one to take it?"

"It's fine Futaba. I think it would be a really special experience to be deflowered by my sister's cock. How many people have that kind of opportunity?"

"Silly Fuka. Call me big sister during?"

"You're born a few minutes ahead and you've wanted to be called big sister since. Sure."

She carefully lined up the tip, trying to take things slow, but I thrusted into her, pushing her all the way into her sister. As I gave Futaba the kind of rough fucking she clearly enjoyed, it transferred into a rough fucking for Fuka, which she quickly started to enjoy.

"This feeling is unbelievable. I feel you reaching to kiss the entrance to my womb while I pound against my sister's, trying to enter her womb."

"Big sister, you're so big, sister. Fuck my womb and spray your cum in there directly."

It looked like she might just accomplish that, and I kept up on my end, pushing deep and hard as well as groping both of their right tits, then both their left ones. Fuka made a lewd face like her brain was getting fucked out, so I guess Futaba did it, and my own orgasm wasn't far behind as we raced to fill up who we were fucking. I came right before her second load, and Futaba ended up leaking cum out of both her genitals. Fuka nearly passed out on me as I wiped her pussy a bit, but she perked back up when I stuck my dick in her.

"Oh, fuck! I just came harder than I thought possible so I'm still sensitive. Have mercy."

"Now now, everyone's getting a turn, and I'm running out of time. If you could handle that, you can handle me."

"If it makes you feel better, the ridge of the head rubs against my G-spot nicely. I'm not just saying that because hers was longer."

"I know. Futaba has the same G-spot location. I figured out what I'm doing from experience."

"Mmm, good then."

Futaba got up, and started cleaning up after herself. She was about to move on to preparing to clean the earlier mess when she started some small talk.

"Relax, I'm not going to give you any surprise butt sex, unless you ask for it."

"Definitely not."

"Just kidding. I'm pretty spent. I can cum three or four times before it turns back if I want, but I was cumming from two sides so it's already back to normal."

That wasn't entirely reassuring, but I could trust she wouldn't try any funny business. It bought me a few minutes, but eventually I blew my second to last load giving Fuka a facial Futaba cleaned with her tongue. As I made my way up the mast, I heard some female voyeur masturbating.