A bet is a bet, so yes

"Now, go get changed," he said, pointing towards the small bathroom. You just sigh, conceding defeat. You never were much of a fighter, so even though you really, really did not want to do this, you stood nonetheless and headed for the bathroom. You shut the door and lock, then you stare at yourself in the mirror holding all of those clothes. You think to yourself just how ugly of a girl you will make, but then you shrug. "If this is what he wants, whatever," you say to yourself in a tone of indifference.

You slowly strip out of your own clothes, taking your time just to delay the inevitable. First goes your Pink Floyd t-shirt, then your jeans, then your boxer shorts, and of course your shoes and socks. Finally, you are naked. Before you can even start, though, you hear a knock at the door. "What is it?" you ask with a tinge of frustration.

"I think you'll need these too. I'm leaving them beside the door," you hear Mathew say. What could it be now? Another piece of humiliating clothing? Once your hear his footsteps leading away, you crack the door open and blindly reach out, grabbing what was there. You shut the door and examine the new objects. Two of them. And you could not believe what they were. They were breast inserts! Fleshly feeling breast inserts for the bra! Apparently Mathew's sister was not as large chested as you thought. So, he wanted you to wear those as well. You just sigh and sit them aside for now.

"Guess I need to start with these," you say to yourself, picking up the bra and panties. First, you wrap the bra around your chest and attempt to snap it. It takes several tries and you almost curse. You have no clue how women did it. But you eventually got it. You next slide the panties up your legs. The feel of the silk actually makes your flesh quiver, you have to admit. You pull them in place over your cock, which is starting to twitch to life. Your cock was never huge, but it was not small either. About 5 to 6 inches, you guessed--you were never the type of guy to measure it. It was at least 3 inches now, embarrassingly enough. If Mathew saw that dressing like this made you horny, you would never hear the end of it. You did the only thing you could think of doing to fix it. You tucked it between your legs. Thankfully, the panties were tight enough to keep it tucked.

Next, you grabbed the inserts and slid them into place, actually filling the bra out now. When you looked at yourself in the mirror, you were impressed to see that you were starting to actually look like a girl. You had what appeared to be breasts and your crotch was smooth where a penis should be. As impressed as you were though, it frightened you too. It would be all the more humiliating if Mathew saw you like this than it would be if your were just some failed attempt at crossdressing.

You cursed yourself for finally finding something you were successful at. But you knew you had to go on with it. So, next, you took a seat on the toilet and grabbed the stockings. You put them on the way you had seen girls do it on TV, by first balling them up, bringing your leg up in a bend, and sliding in with the tip of your foot. It worked a lot better than your first attempt to put on the bra. Before you knew it, the stockings were up to your thighs. They were the sort to have a lacey area that wrapped right around your upper legs. You ran your hand over both legs to smooth out any wrinkles. You have no idea why you bothered, but when you did, you found that your legs luxuriously smooth. It was rather nice.

Next, you quickly slide the skirt up your legs, buttoning it in place, and then slid your arms through the blouse and did the same. You had little trouble with these last two items. You stood at looked at yourself in the mirror and saw what by all accounts would be a babe. The only thing missing was some makeup, but there was already enough rouge in your cheeks from blushing.

You took a deep breath and grabbed the door nob, opening it, and finally stepping outside the bathroom.