I've been dating my girlfriend Miku for two years. She's serious and old-fashioned—so much so that she won't even let me kiss her, which sometimes makes me feel a bit lonely, but I accept it as part of her personality. One day, I hear that Miku is going to celebrate my birthday with her best friend Hikaru, so I head over to her place excitedly. I was hoping to spend the day alone with Miku, but being surrounded by two girls feels awkwardly thrilling. Still, I'm in a good mood. Shortly after the birthday party begins, Miku leaves to get some alcohol, leaving me alone with Hikaru. Suddenly, she starts seducing me—giving me a bold tongue kiss. I'm confused, but my body reacts instantly with an erection. Hikaru smiles mischievously, clearly enjoying my reaction. Even after Miku returns, Hikaru casually continues chatting, her playful demeanor like a little devil. Soon, her leg sneaks under the table and starts teasing my crotch. "You absolutely mustn't make a sound," she whispers. I know it's wrong, but my body surrenders to pleasure. Then, right next to sleeping Miku, I start grinding against Hikaru, muffling my moans as I'm driven into a reverse rape frenzy. Sorry, Miku... but it's my birthday today, so this should be allowed... right!?