Sure, let's see what it is

"Really?" Emily says, getting really excited. The short futa jumps up and down, clapping her hands, only to blush furiously right after, embarrassed by her outburst. "I mean, that's cool. This way!"

She leads you into the house, so excited about this thing she is going to show you that she even forgets her offer for tea. "So, have you read Doctor Simmens' recent paper? She talked about latent epigenetic triggers in the Z chromosome, you know the futa chromosome. She theorized we could use these triggers to create large changes in futa bodies, to treat various genetic diseases and hormonal deficiencies. I recreated her experiment with my own DNA and I found many more latent triggers than she listed, so I started experimenting with some cultures and..."

Her rapid fire scientific explanation is leaving your brain a little fried. One of the very few perks of being a male is that no teacher expects you to actually understand the material, so most just give an arbitrary pass, and many guys are happy to accept it. Still, it is nice to see her so eager and excited. Her smile is captivating.

Finally, you enter her room, half of which is occupied by a huge desk covered in scientific equipment. "... So I changed the chemical balance of the main signal proteins and that's when I got my breakthrough!" It is only now that she realizes she lost you. She sigh, but her smile does not go away. "Sorry, I got carried away. In a few words, I think I managed to create a... well a growth serum. It should trigger something like a second puberty, at least in theory."

"Wait really? Is that your plan?" You say, worried and intrigued at the same time.
"Yeah, but I didn't want to try alone, but I don't really have friends and my family would never understand. I thought... I thought you as a male could understand how much it sucks to be small and weak." She looks at you with hope in her eyes, craving your approval and understanding. It is so weird to see a futa looking a you that way.

"I guess I do. Ok, what should I do?" You say.
"Yes!" She screams, hugging you suddenly. Her head leans against your shoulders, while her bulge rubs against your thigh. "Just keep an eye on me. If anything goes wrong, call an ambulance, but only in a real emergency, mom would kill me if I got to the hospital for nothing."

Without further hesitation, she takes a syringe and fills it up with a weird blueish liquid. "Well... the die is cast." And with that, she injects the liquid into her forearm.