He's shocked of course, but incredibly helpful afterwards

You close your eyes, not wanting to see whatever reaction he has on his face when he comes in. Would he be shocked? Of course, he'd be shocked after seeing a girl replace his middle brother. Or would he pretend if nothing significant happened? Was there a chance that he'd think that you've been a girl this whole time? Before you can form any more theories and predictions, you hear the sounds of his steps briskly make their way up the stairs. The doorknob twists and removes the bolt from the doorframe and the door itself opens inward. “You're lucky I have a day off today. What does my little brother need this--?” he starts to say as the door swing open. His question abruptly stops when he obviously sees a girl sitting on his bed, with no sign of his brother in the room. You open your eyes slowly, a predictable expression of shock on his facial features. You give him an uneasy smile.

His eyes dart across the room. “John?” he calls out, as if his little brother may be hiding somewhere. His eyes investigate the other corners of the room. Initially, he obviously doesn't consider you, currently a female, to be his brother. “Did you text me because you needed some condoms?”

You put two and two together. He probably thinks you are your new girlfriend and responsible big brother thinks only he could be a help in his little brother's time of need. No way his brother John would ever call his sister or even the runt of the family for such a need.

You feel like you shouldn't keep your older brother in the dark any longer. He came here to help you. He at least needs to know what situation you have found yourself in. “Jake,” you address him. His attention is now solely on you. “I'm John.”

He has a confused look on his face. The girl in your room stated that she was in fact his little brother John. He's probably asking, 'How can that be?'

You speak, completely aware your voice is higher in pitch. “This morning I had a mysterious phone call. He... she?... it?... made me aware of my new body,” you start to explain, presenting your female body and then getting to your feet. You notice how much taller your older brother is to you. You can't help but turn your gaze upward to meet his own. “The caller said I was stuck like this for the next 48 hours.”

His expression reads like he is trying to put the pieces of the puzzle together. He doesn't understand how things came to be, but somehow most of his focus is on what needs to be helped rather than getting to the bottom of why. “I'm assuming you change back into John after 48 hours. What happens if you don't?”

“The voice mentioned that this body is fertile. Very fertile, emphasis on 'very.' I'm guessing the chances of me getting pregnant is high,” you mention.

“If you conceive, then the female body is permanent. And the only way you could conceive is by having sex--” he continues and adds and you chime in by finishing his sentence with a crude phrase.

“...and the guy doesn't pull out.”

“That's one way to say it,” he mentions. “So, whatever you do, just don't have sex. Easy answer.”

You slump back down onto the bed, going so far to lay across it. Jake walks over to sit next you, his attention still on you. “There was something else the voice said. It said I couldn't simply lock myself at home, as this body will demand some attention. Pretty soon, if I might add.” You sit up, looking to your older brother. “I don't know what that means. The caller kept that very vague. And it ended the call by saying people will be more than happy to help me with that attention, whatever that means.”

“Don't worry. We'll figure this out,” Jake assures you, placing a hand on your shoulder. Somehow, you believe that he believes you are John, his little brother. “Okay, how about we start with how you feel? The call said your body would demand attention somehow. How would you know if your body doesn't tell you in words?”

“There would be a symptom, like if I'm sick, I would have a sore throat, a cough, or a fever,” you reply, glad that your older brother is here to help you investigate the root cause of this matter.

“Right. So, are you feeling any symptoms? Anything you feel that is off or significant?”