The metro car is filled with the hum of the train and the quiet whispers of passengers, but Zen's focus is singular. She's mastered the art of fellatio, and today, she's practicing in public. Her partner, a stranger, stands before her, his cock out, his hands gripping the pole for support. The train's movement rocks them, intensifying the sensation. Zen's lips are sealed around him, her cheeks hollowed, her eyes closed in ecstasy. The train stops, passengers disembark, but Zen doesn't falter. She's in her element, lost in the rhythm of the train and the throbbing pulse in her mouth.