Call her bluff

You reach down and cup Mina's face in one hand. "Well, how about it?" you ask with a smirk. "You said you don't have classes tomorrow, and you'll be mostly drained out by the next day, right? Unless someone fills you back up before then..."

Mina's blush becomes even more pronounced, and she mewls something inaudible as she shifts a little closer to your rapidly hardening cock. "What was that? I couldn't quite hear you," you taunt as you see her reach down to stroke her folds.

"Do it. Fuck my brains out," she whispers. In a second you're back to full arousal, and you line your erection up with Mina's ear before grabbing the back of her head with your other hand. A guttural moan escapes her lips as your cockhead defies all logic and squeezes into her earhole, turning into a squeak as you thrust into her head. You feel her brain, already basically floating in a pool of cum, give way to your cock and melt into spooge; as it does, Mina's vocalizations increase in frequency and go from almost pained yelps to breathy begging. "Jesus Christ, your cock - fuck me harder, please, I wanna be a dumb slut -" You glance over to the couch and are unsurprised to see Lily biting her lip and furiously masturbating.

Between both your friends' moans and the feeling of fucking Mina's head, you orgasm again, a lot harder this time. You feel the blast of jizz melt down the rest of Mina's brain as she twitches against your legs, and as you cum more, you feel slight pressure starting to build up around your cock until it bursts. Cum pours out of Mina's nose and ears, as well as oozing out of her mouth. As you pull out of her ear, she seems to become a bit more lucid and looks around confused. "Uh... hi, Alex, Lily. Like, what's going on? I feel funny."

Lily speaks up from the couch. "You - hnf - you wanted Alex to brainfuck you."

Mina frowns. "That doesn't sound right..." She furrows her brow for a second, then breaks into a grin and shrugs. "Oh well, I'll figure it out later. It's Halloween, right? I wanna go get fucked!"

Lily reluctantly stops stroking herself and gets up from the couch. "Okay, I'm gonna go change into my costume. Alex, you're gonna change too, right?"

You scoff, heading to your room. "Like I'm gonna be this excited for Halloween and not have my costume ready. I'll be out in a minute or two."