The screen sort of answers your question by displaying another message- "PHASE 2: FEMINISATION", it says. A similar tube to the one which wrapped around your cock moves towards your mouth, and the smell and texture of it is weirdly enticing. You open your mouth and it slides inside, and as you suck on it a liquid flows down your throat and you swallow it repeatedly. It tastes oddly salty, but sort of nice.
You realize something has started to shift in your head from this process. Sucking that thing like a cock felt oddly natural, even though you've never considered yourself gay before. Actually, what really strikes you is the idea of attraction to men doesn't seem gay anymore. You feel oddly detached from the idea of being a boy. And when you look down at your body, it looks distinctly less boyish and more girlish. Your thighs seem rounder, your skin softer, your hands and feet more petite.
And it proceeds to get still more girlish. Your nipples enlarge and perk up, and as you breathe heavily in a higher-pitched tone than you're used to, you see flesh start to swell around them. You idly fantasize about someone's big, firm hands cupping them, rubbing them, pinching them, their mouth licking, sucking, biting them. Part of you protests- but these are breasts! Boys don't have breasts!- and you just realize, you're not a boy anymore. You're a girl, or at least nearly a girl.
You look down and see your penis has started to shrink away. You rationalize it pretty fast- you ejaculated away all your cum, so now you don't need one anymore. Soon, you'll have a vagina that can be fucked and you can get pregnant from! Won't that be cool?
After moving inside you, your testicles are converted by your body into ovaries, and your scrotum tucks inwards until you only have a slight mound between your legs. Something deep inside you connects up with it and you feel your body open down there as vaginal lips form at the mound's centre. What remains of your penis reaches its tiny feminine size and massive feminine sensitiveness and turns into a clitoral hood.
You look down at yourself in amazement. Wow. You never realized 'female anatomy' didn't just mean having a vagina instead of a penis, but being turned into basically a female version of yourself! Having said that, you kinda like it that way. At least you aren't gonna feel weirdly incomplete.
You wonder if there'll be another phase or if you're free to go...