After you find the text of the spell in your brother's, it takes you a few moments to stop and think about what you really and truly want from this moment on. You were never as desperate to become an animal as he seemed to be. Supposedly, he eventually ended up with an old friend, wandering the aisles of a shop he'd never noticed before, and they'd both found so-called magical spells for sale. They'd pooled their money together to by a copy of the permanent animal transformation spell. After the friend turned into a bird and flew away for ever, your brother realized it was the real deal, turned himself into a wolf while making a goodbye video, and that was that.
As for you, holding his journal, still looking over its last few entries, including the bought-and-paid-for words of the spell, you now have a choice to make. Can you really just leave your life behind you like he did? You weren't married and didn't have any kids, but you'd made a lot of really good friends at work that you would miss. You'd be putting your parents and extended family through a second disappearance in just a week. The cops would scour the keep looking for evidence in a cold case probably forever. You'd never make any money, wear any new clothes, visit any more bars, attend any more concerts, or do any more human things if this happened. Naturally, you could never tell anyone else, just like your brother couldn't tell anyone except you, because your family would be devastated to know that you'd voluntarily given away your human life to live as some wild animal. Besides, what would happen to society if a high profile investigation revealed to the entire public that magic was actually real?
You're closer to your brother than anyone else in you family, though. He was the only one who understood your desire to live as an animal, and you were the only one who understood his. You were always telling each other that if you had the chance to be wolves, you would take it in a heartbeat. Now that it's actually a real possibility, it's not quite that easy for you, but you decide it's worth it. You would give up anything to have another chance to be with your brother. You destroy the tape, burn your brother's journal, and send one last letter to your parents to say that you're okay and are leaving to start a new life. You take the words of the spell out in the woods with you on a post-it note, take off your clothes, and read the words out-loud under the moonlight. Your ears tear up in joy when gray hairs sprout from your skin.
You look down to watch your clit swell out and take on more the shape of a male organ. It's small at first, but it's yours, and you couldn't be happier. You're as thrilled as your brother was about the fact that this spell changes one's species as well as one's sex. Neither of you could have ever come out to your transphobic parents about your gender dysphoria. Now here you are, growing a penis the same way your former brother (now sister) lost his. A pair of round organs starts shifting and lowering within you, before finally spilling out into a newly formed sack underneath your groin. Fondling your newfound scrotum, finally experiencing what a man does, you start to feel a tightness in your one-inch penis. It's hardening, swelling up to two inches--your first erection! Jiggling it between your fingers to play with it, you end up accidentally scratching your sensitive new flesh with pointier fingernails. This makes you yelp in pain, but it does give you a reason to look at your fingers and discover the beginnings of sharp claws sprouting from your fingers!
You touch your large breasts with padded hands one last time as they start to shrink away, remembering how much you hated going through female puberty and watching yourself start to look like more of a woman, when you always wanted to be a male canine. Soon you don't even have any noticeable breasts at all, just a pair of very small nipples sticking out of your chest, but you soon sprout a lot more new nipples down your belly. They may be useless now that you're never going to breastfeed a baby or suckle a litter, but they remain a sensitive part of your body that your rough pads stimulate in arousing ways. Your dick and balls really kick into action as you seem to go through a kind of male puberty within seconds: your balls swell and grow more hair (which quickly becomes gray fur), and your dick (already hard) starts stretching forward in front of you, bulging out to about three times its size until it's at least six inches, maybe seven or eight. You can wrap your whole hand around the thing now, and stroking it sends shudders of pleasures all the way up and down your spine.
Once you start settling into a decent rhythm like a man learning to masturbate, you start to feel liquid pooling in the little hole on the far end of your new organ. You sniff the air with an increasingly moist nose: precum! Something makes you think to bend down there and try to lap up that new liquid, as though your tongue could reach it down there, and to your surprise, it can! Your face has been getting longer while you've been trying out the new genitalia you've always wanted. More importantly, your tongue has gotten longer, and wider to, you realize, at it slurps over your glans, giving you tastes of the musky scent you've found yourself craving. You're tailbone cracks and starts to wiggle slightly at the end of your back, giving you a tantalizing foretaste of what it will soon feel like to wag a complete tail.
Before you can get fully acquainted with the male genitalia you've always envied on previous boyfriends, a piercing feeling jolts through it, making you yowl into the night like an animal that's been shot. You hope you're not going to lose your new dick already! But no, you're just obtaining something your boyfriends never had: an actual boner in the literal sense of the term. Your dick, harder than it's ever been this whole time, is getting a lot veinier and has forfeited the unique glans shape that human males take for granted. Pinching your dick carefully, you can feel a firm rod of bone deep inside it, the penis bone that only humans and horses have to do without. You start licking again and notice you can taste fur growing on a loose sleeve of skin enveloping the base of your new wolf cock. Soon, that sleeve of sorts reaches back and fuses into your furry belly, giving you pocket-like penis sheath that every male dog you've seen carries between its hind legs. It's amazing that all your secret late-night studies of canine anatomy are starting to pay off.
Your new genitals can't withstand your constant stimulation any longer, and your body clenches up while you start to feel warm fluid pooling inside you very close to your bladder. It almost feels like you're about to urinate, but you understand what's really about to happen. A sudden muscle spasm lets go of a small sample of the liquid and shoves it up into your penis and then out through the tip. More spams make your insides tingle and your dick squirt hot liquid into the moonlight. Something round is starting to ball up at the base of your penis, and you make desperate contact with your new knot even as you're already nearly blinded from the pleasure of real semen pulsing through inches of male meat that are yours to enjoy from now on. Your long doggy tongue laps up some of the fountain before just lolling out front in ecstasy. Your thumbs go numb and your fingers lose their ability to grip anything, but you just sit there, dangling your forepaws in the air, waiting for your male orgasm to die down. You keep cumming for longer than any boyfriend you've ever sucked off. You think your male prowess is going to be very satisfying for a female wolf someday.
By the time your flow slows to a trickle, you're on all fours shifting your legs around trying to into a decent four-legged stance while your tiptoes become clawed paws like your fingers. Some shifts in your spine and leg bones help you make that happen. Your ears start to flick around, taking in the sounds of the forest. You hear a wolf somewhere, wondering if it might be your sister. A powerful new appendage starts swinging from side to side beyond the confines of the old you, so you look back and take a few moments to admire the tail you have grown. Your new maleness slowly tucks itself backward into the skin that has become your sheath, and you raise your head to the moon and howl with your new voice into the night.