Based on the picture "Femme Shanks and Mihawk" by pinki100 on deviant art.
The first thing that Shanks was aware of was the hangover. Those were always rather assertive upon waking. The second thing he noticed was that the usual, comforting weight of his equipment against his thigh was missing, replaced by a small and gentle itchy feeling that he would definitely be investigating when the hangover faded enough to let him panic over the loss of his usual piece. The third thing he noticed was that there was a weight on his chest and that his nipples – things he usually gave no thought to at all – were rather sensitive and a bit tingly. The fourth thing he noticed was that he had his left arm back again, which was nice even if it was tingling with that pins-and-needles feeling at the moment.
If it hadn't been for the hangover, Shanks would have thought he was dreaming. But it was there, which meant that whatever was going on wasn't a dream, which meant he should probably peel his eyes open and see what had actually happened.
Hm. There seemed to be a piece of paper over his face, and possibly something written on it, though it was currently too close to be read.
Moving slowly, Shanks picked up the paper and drew it away from his face until he could focus on whatever was written there. As he read, he became aware of a different feeling. A sort of hollowness between his legs that was further down than where his usual parts rested.
No, you're not going to stay a woman, it will come and go a bit over the next twenty-four hours. I also gave you your arm back and left you some company. This is not a favour, you don't owe me anything, I lost a bet. After the twenty-four hours you will be back to just the way you were before that run in with the Sea King all those years ago.
The note didn't mention anything about the scar over his eye though, so Shanks decided to haul him- er, herself out of bed and find a mirror. He, dammit, she would probably need to adjust his – her – clothing around the recent losses and gains too.
The scar was still there. The breasts were rather nice, the legs (and a few other areas) had apparently been waxed or very well shaved while he was out of it, and for a moment Shanks thought about if he'd get friendly with a woman that looked like he did now if he was still himself, which in turn led to thinking about what would happen if he found the other person Ivankov had left him as 'company'...
Said 'company' had also woken up to a set of excessively similar circumstances, including an almost identical note, and had by this point checked the mirror already and adjusted his, now her, wardrobe accordingly. A moment of thankfulness had passed when it was discovered that she could still lift her sword just as easily as he ever could, and wasn't that confusing, and then she was out the door of the room she had been left in and blinded by painful sunlight.
Yeah, she was hung over too. Odd, since normally he didn't drink to the point of getting drunk and therefore getting a hangover, but hung over she was.
Or maybe that was a side-effect of Iva's meddling. Like the loss of his beard and moustache, and in fact every hair that had been on his body from nose to toes. God, that was embarrassing if it had been shaved or waxed off by a person, and not just Iva's messing about with his person, which was frankly creepy enough. No hair except for the (thankfully still short) black locks on his, dammit, her head. Hell, she should probably be glad the okama hadn't used curlers on him. Her! Damn it!
The pain of the sun faded, slowly, but it faded, and by the time she could see again another person had emerged from the next hut.
An attractive person, and Mihawk smiled to him-, dammit, herself in appreciation of that fact. It was commonly supposed that Mihawk was capable of stripping a woman of her virginity simply by looking at her. This was not true. What was also not true but commonly supposed was that Mihawk could charm any woman into his bed that he wanted. It was never supposed, but completely true, that in fact Mihawk was just a little bit of a romantic and believed in things like chemistry between two people and growing old with that one special person.
Even the scar over her left eye didn't take away from how pretty she was...
Wait. That scar looked familiar.
"Shanks?" Mihawk asked, yellow eyes growing a little wide in shock.
The red-head nodded, her pretty jaw dropping as she took in Mihawk's current appearance.
"Hawk-eyes?" she asked.
Mihawk nodded, then swallowed nervously before taking a few steps closer to the other – actually male – person.
For a while, they just looked at each other. Up and down, raising hands to touch but not actually touching, until Shanks broke their shocked silence.
"Oh screw it," she said, then wrapped delicate hands around Mihawk's neck and pulled her into a very passionate kiss.
The two women had a lot of difficulty figuring out exactly how to draw orgasms from their new bodies, but they figured it out. Then Mihawk turned back into a guy. There was a moment of uncertainty, if Shanks would be alright with the change – straight men in women's bodies wasn't the same issue, but this was an alteration of orientation. The moment passed when Shanks smiled and said she'd get to be the first one to find out if it was a different feeling to fingers. It was of course, and then Mihawk was a woman again and Shanks a man.
Shanks had whispered "My turn," into Mihawk's ear before putting everything he had learned so far about how female bodies reacted into practice – by making love to Mihawk.
After three rounds, the two of them fell asleep, curled up together on the bed. When they woke up again they were both men, and Mihawk was very surprised – though equally pleased – when Shanks kissed him. The two of them spent a good few hours learning how to make love as two men.
Of course, there would probably be issues with the World Government, not to mention Shanks' crew and finding out just who Iva had lost a bet with that had gotten them into this situation.
But the best things in life are worth fighting for...
~Really the End~