I had just turned nineteen and was staying with my Grandma while I went for an interview for a place at university. Finances were tight and staying in her spare room for a couple of days, giving her a little money for my food and board made a lot of sense.
I was only going to be there for the interview and then I would find a flat with a couple of other students, if I was offered a place. In the meantime, she cooked and made sure I had a clean shirt. The day before she had fussed over me, making sure that I was neatly dressed and my shoes were polished, so that I would make a good impression on the interview panel.
This morning, however, I was just waiting for the result of my interview. With no particular hurry to get up I lay on top of the bed in Gran's spare room and, eyes closed, was slowly stroking the length of my cock which. Most mornings would see me waking up with a throbbing erection and this morning was not breaking the pattern.
It felt so good to leisurely stroke my hard cock that I was soon lost in my own little world, centred around my stiff cock and the pleasures of a relaxed, gentle wank. My eyes were closed and my ears filled with the sound of my own breathing, so I never noticed the door slowly opening. I heard a soft gasp and guiltily opened my eyes, to see Gran, in her housecoat, watching me slowly wanking.
Blushing, I tried to hide my cock, and my embarrassment, behind my hands. Unfortunately I had only managed to get my cock fully erect and there was no way that it was going to subside, unless I finished my wank. Gran just stood in the door for a moment and then stepped inside the room, closing the door behind her.
I was puzzled and amazed. Gran was moving closer, until she was able to perch on the edge of my bed. Her housecoat fell open, a little way, displaying a deep cleft between her breasts as they hung down, heavy and ripe.
"You shouldn't stop," she told me, "or you might do yourself a mischief. Here let me help you."
As she spoke, she lifted my hands away from my cock and balls and wrapped her own fingers around my shaft. Her hand was warm and dry as she stroked me with gentle, expert motions. Every couple of strokes, she would curl her fingers around my balls, gently hefting my sac and smiling as she felt the weight of my balls. I knew that I ought to stop her but it felt so good that I said nothing and lay back, enjoying the feel of her hand upon my swollen knob.
"Oh, you naughty boy," she whispered, "hiding your beautiful cock from your Gran."