Amber

"Yeah. I'll be done in a minute!" You yell to the person who knocked on the door.

Lost in the pleasure of your furious masturbating, combined with the roar of the jets of water, you didn't see or hear the bathroom door slowly open. You were completely unaware of Amber's presence as she stealthily entered the bathroom and closed the bathroom door behind her. Only when she flung back the slide door of the shower, catching you furiously beating your meat, were you aware of her.

"Oh shit, Amber," you cry, desperately trying to cover your modesty and hide the fact that you have been masturbating. It is clear from the look on her face that you have failed utterly in the latter.