"Join" him in the shower

You sneak behind him as he heads towards the master bedroom. Your parent's room. Of course he'd use the master bath.

You hide outside the room watching him undress, his cock swinging loose from his shorts as he walks into the bathroom.

You now enter the bedroom, right outside the door as you slip the ring over your hole. It appears on the wall in the shower, right as your dad enters. He turns on the water, and begins to soap up, paying special attention to his cock, eyeing the pecker on the wall. You feel him press a finger against it, covered in soap it slips right in. A second one follows, then a third. All the while, his other hand is stroking his growing manhood, intermittently washing his body. He was here to clean up, after all.

He positions himself so his dick aligns with your hole, and shoves it in. Hard. The sudden pressure in your ass is breathtaking, and pleasure only increases as he begins to thrust in and out, slamming into your prostate and grunting with lust each time. You feel your own orgasm approaching as he picks up the pace, until finally he lodges firmly in your ass, his pubes gently scratching you as he unloads his second load today deep in your ass. You also came, leaving your pants as stained as his shirt behind you, although a different substance.

You watch as he finishes showering, and contemplate leaving him behind.