Harry Potter – “Transition Potion”

Disclaimer: I do not own the characters –except the main one- or the universe, J.K. Rowling does.  I merely play with them.

Alternate Universe

Rating: M + – NC17

Pairing: Other Character/Sirius Black

Warning: genderqueer, sex transformation, m/m sex.


She was in the room she usually slept in 12, Grimauld Place, when Sirius barged in.

“Oops! Sorry, I thought you were already down for breakfast.”

She was wearing a tshirt and “Are those men boxers?”

She sort of blushed “Yes…Why?”

“Why do you wear men boxers?”

She put on her jeans “Because…they’re comfier?” Seeing his unconvinced look, she decided to come clean “Because I want to be a boy and I like wearing boys’ clothes.”

He looked surprised, then “Why do you want to be a boy?”

“Because having the body of a girl doesn’t feel right, like it’s not me. Sometimes it does though, that’s why I never transitioned.” Seeing his confused look she explained “Muggles who want to change sex have to have surgery and injections of hormones for the rest of their lives. It’s a lot to go through.”

“You’re serious? You have to do all that? Just go talk to Snape, I bet he’ll have a potion for you.”

“Erm… Thanks Sirius, I’ll do that.”



“Yes, what is it?”

She looked around to check all the students were out of the room “I was wondering if there was a potion to…erm… change sex?”

He stared for a moment “To what?”

She was getting nervous then “Well, I would like to become a boy, but in the muggle world it mean surgery and such and I don’t want to do it permanently, and I told Sirius and he said to ask you…”

He had gotten up and was looking at a book from his library by the end of her explanation.

“Ah, there it is… mmh… I appear to have everything I need… Come back tonight and I’ll have it done.”

“Oh. Thank you! How long will it last for?”

“A month. When was your last…erm…”

“Last week…”

“Until the next ones.”

“OK. Thank you Professor.”


Once she had got her potion from Snape, she went over to Sirius. Since it was his idea in the first place, she wanted him to be there when she changed.

“I really hope it doesn’t hurt.” She was looking at the bottle anxiously.

“You won’t know until you’ve tried. Go on. I’m here, I’m not going anywhere.”

She took a deep breath and swallowed the content of the vial.

“Eww! That taste fowl!”

Her body started to change, internal organs moving, chest receding. It wasn’t painful as such but not nice to feel. Soon enough..

“Wow, I’d never seen anyone take it, it’s really impressive!”

She looked down and “I’m flat chested! This is awesome! And… I fill my boxers now!” He took his t-shirt off to look at his now flat chest, with just a thin path of dark hair leading to inside his jeans.

“I think you should go to your room, you know, get time to…know each other.” Sirius winked at him.

“Yea, you’re right.” He nearly ran upstairs.


He was on his bed, the room only lit by the light coming in from the window. He was kneeling, head in the pillow to muffle his moans as he caressed himself. He thought he’d imagine the noise of the door creaking open, but he knew he hadn’t when he felt the mattress dip as someone climbed behind him. He raised his head and looked behind him to see Sirius, wearing only pyjamas bottoms; tented pyjamas bottom.

“Sorry if I scared you” he murmured “I couldn’t help hearing your moans and… I had to come help you. If you want a hand, of course.”

The young man could only nod and his hand was replaced by Sirius. He leaned against him as he caressed him, uttering soft moans and moving his hips in time. Soon, he slid his hand between them and returned the favour, earning himself a nice growl.

As they caressed each other, Sirius nibbled on his ear and neck, making him whimper. Then, he held a finger to his mouth to suck. Once wet, the finger found its way to his opening and he lowered his head on the pillow once more, abandoning himself to the man behind him.

Soon, a finger was replaced by two, then by a third.

“Sir..ius…aah…I…don’t think I have…You know…Since I’m not really … Ah!”

Sirius chuckled “You didn’t think you had this?”


“The potion changes you fully. Relax and enjoy”

“More…I…aah…want you…”

The man quite happily obliged, spitting in his hand to use as lubricant.

“Have you ever done it before?”

“Yes. Just not recently.”

“I’ll be gentle.”

He slid in only the head, first, to let the younger man get used to it. Then, slowly, he moved further with each trust.

“Oh god! Sirius! More … I… Ah!”

“There! Found it”

After that, the young man stopped talking coherently, only babbling and moaning in pleasure until

“Sirius… I…Oh god…” His whole body tensed as he let out a loud moan. He came all over Sirius’s hand as the other man followed him in pleasure.

They collapsed on the bed, Sirius careful not to crush the smaller man.

“God…That was amazing…”

“Like you had imagined it?”

“No, better! I’m going to love this potion I think. Erm… I have a couple of questions…”

Snuggling close “Ask away, I’m not going anywhere.”

“Erm… I really like you and…I’d like to see you again…as in…”

Sirius cut him “As in have a relationship. I think I would like that too… What was the other question?” He nuzzled him.

“I have to stop the potion one week a month, will you be ok with it?”

“Yes. And I’d be ok if you decided not to take it, or just from time to time. I like you, as a person, not as a body. Although, I must admit, I like the body too, both actually…”

They fell asleep snuggled up against each other.

The End


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