Even though your whole body just changed, one thing that's the same is your horniness. Except it's adjusted to fit your new form. Images of handsome, naked men fill your mind, and you're picturing yourself lying down and spreading your legs for them and...
OK, focus, you tell yourself. You just transformed into a girl because you wore that yukata. So... maybe if you tried putting your old clothes back on, you'd turn back into a boy? That sounded like a good idea! Hastily, you pulled your jeans and T-shirt out of the bag, and pulled them on. You were surprised how much bigger they were on your new form, but you could just about still wear them. Looking in the mirror, you start to worry. You're not changing back. Suddenly your nose picks up on something. These clothes... they still smell like a boy.
You feel an intense warmth in your chest and between your legs. You suddenly realize your nipples are suddenly hard and sensitive, and between your legs your new slit has moistened. When you try to yank off the shirt, it rubs against your nipples and you have to bite your lip to keep from moaning as an intense ripple of pleasure rushes through you.
It starts to make sense to you what's happened to your sexuality, if nothing else. You were a straight boy, so when you changed sex, your sexual preference stayed straight. That's why you're attracted to boys now.
And fuck are you attracted to boys. The scent is overpowering you, and soon you lie on the bed, slide your hand into your jeans and start grinding against it. Your other hand grabs at your chest and cups your boobs and rubs your nipples through the fabric, a whole host of fantasies filling your mind. You imagine boys sucking on or grabbing at your tits as they fuck you, their balls slapping you, their bodies aching to fill you with cum. You imagine sucking their cocks, getting face fucked as they hold your head steady and fuck your throat with their firm shaft, railing you until you need air and letting you breathe while they rub themselves, guaranteed to cum either in your mouth or on you.
Part of you is even getting off at the thought of your recent transformation. Less than an hour ago you were a boy, you had a cock, a body designed to fuck and fill others with seed. Now you've been reconfigured, and you're a girl, you have a pussy and tits, a body designed to be fucked and filled with seed. Are you getting a fetish for how you were transformed or something? you wonder.
And before you know it, you're cumming. Hard. You gasp, and everything seems to go fuzzy for a minute. When you come down from the high, you slowly realize what you just came from, and your senses slowly start to return. So, changing back won't be as simple as putting your old clothes back on, then...