Masturbating

As you open, you find her undressed, using two fingers to play with her pussy
As she sees you she gets bright red... but, at the same time, you notice her nipples getting hard
"John! get out of here!"
You stutter, trying to look nervous
"Sorry, sis... I didn't intend to..." Then you leave the room with a big smile and go towards the kitchen... maybe you can still have some fun with your parents...