In a dimly lit room, a Mistress stands over her bisexual slave, a smirk playing on her lips. She holds up a massive dildo, twirling it in her fingers, her eyes never leaving her slave's. "You want to take a real cock up your ass, don't you, slut?" she purrs. The slave nods, their eyes wide with anticipation and fear. The Mistress laughs, a low, cruel sound, and presses the dildo against the slave's asshole. She pushes, slowly, letting the slave feel every inch, until it's buried deep inside them. Then, she begins to fuck them, hard, using the dildo to train their ass for the real thing.