Yes/Chad/Just help her with her confidence and see what happens
The girl just lacks confidence. With added self-confidence, you're sure she would start taking more interest in her appearance, and be willing to be more open about what she does and does not want.
"Mina," you say, cautiously phrasing your sentence in your mind before you say it, "from now on you will be confident in yourself. You will know your own worth and limitations, and not be so shy and reserved. Isn't that right?"
"Yes," she says, visibly relaxing and looking you straight in the eye. "How did you do that?"
Damn . . . from now on did that . . . at least you think it did. Let's see, nerdy girl . . . magic or superpowers? . . . Harry Potter or the Avengers? Avengers. You like Tony Stark a hell of a lot more than Dumbledork. "I have superpowers."
"Huh? Oh, haha! Right." She responds, "but no, seriously, it felt like my mind just went dull for a moment and now I feel like what you said is true. It's like some kind of... like... advanced hypnosis or something."
Well, you wouldn't expect her to just accept it that easily. At least she seems to be thinking about it as a joke. Well then, should you go another route or double down? "No, actually I wasn't joking there." Well, looks like it's double down time.
"Ehh.. haha," she laughs a little less confidently than her previously enhanced confidence self. "Ehhh... wait, seriously? Like... Professor Xavier or something?" Bingo! Looks like going with super heroes was the right choice after all . . . though it actually could have been both you suppose.
"More like Superman, but without any of his weaknesses and limitations . . . and with the ability to alter reality in small ways."
"Ok, now I know you're messing with me." She says.
"Nope, I can prove it." You tell her.
"Alright then, what do I have in my pocket?" She takes a challenging demenior that is completely the opposite of the mousy girl who entered this bathroom.
Well then, this should be easy. You use your x-ray vision to look in her pocket, but can't help but check out her body as you're at it. It's a nice body, a little soft for your preference, but not at all plump. Her breasts are quite large, but could use some extra support you imagine as they seem to be tugging her bra down more than you think would be desirable. You also notice that her hymen is intact . . . sweet, a virgin. Oh, yes . . . her pocket.
"A black and white rabbit's foot key chain," you say confidently. Gwen raises her eyebrow, but doesn't say anything.
"No way!" Mina's eyes seem to practically bulge out of her head as she stands there looking stunned. "That's awesome!" She shreeks, bouncing up and down as though she can hardly contain herself in her skin. "Oh my god! Oh my god! You have actual X-ray vision. That is sooo COOL!" She bounces her way over to you, touching your biceps almost as though she is touching a holy object. "What else can you do. You said you could do everything Superman could do without the weaknesses right? So, what are you? An alien? What's your origin story."
"Umm... well... actually, the Superman powers are something I gave myself using my real power, the reality altering one."
Mina lets out a huge gasp at that, almost to the point she seems to stop breathing. "No.. freaking.. way!" She says. "So, like... can you give other people super powers with that ability? You're like... one of the supreme entities or something... like... like... I don't know. Apocolypse? Nooo... couldn't be... You're not going to destroy the world or anything with your powers are you?"
"Nooo!" You say a little stunned she would even suggest such a thing. Although, she really didn't seem serious herself when she said it.
"Hehe, yeah, of course not. I'm just being silly." So... what!? She is just saying whatever's on her mind stream of consciousness style? That sounds a little dangerous.
"Hey," says Gwen, a bit annoyed, "I'm here too."
"Sorry," says Mina as she turns to your sister, "I didn't mean to ignore you, I'm just a huge super hero fan. Maybe this will make it up to you." She nervously pulls Gwen in, and kisses her tentatively on the lips. Gwen pulls her even closer, and takes the lead, kissing and fondling your new friend. The girls make out for a while, waking your cock once more. You watch for a bit as it gradually becomes steamier and steamier. Finally, feeling a little left out, you clear your throat.
They both look up at you, the passion still hot on their lips. "Oh, poor Chad," says Gwen, "do you want in on this?"
You answer her by taking them both in your arms. You kiss Gwen, then Mina, then guide them into a three-way kiss. Well, this is going swimmingly.
What's next?