It was a warm day. Warm enough for me to be wearing shorts and a t-shirt. Mum was wearing bright sundress that stopped about 5 inches above her knees. All day I had been catching glimpses down the front of it when she lent forward, as the top was low cut with a couple of thin shoulder straps. She had big creamy white breasts and her bra barely contained them.
We had finished the shopping and the heat off of the pavement was cruel as we made our way to the bus. We had to make a bit of run for it as it was already waiting at the stop. We managed to make it and I took the bags from mum while she paid for us. I wandered down the aisle to the only free seat. It was next to an old man who was sleeping. Mum followed behind me and stood in the aisle. I offered my seat to her but she politely declined it. We had been travelling for about five minutes when she changed her mind. Taking the bags from my lap, she plonked herself down and turned to me
"I hope you don't mind me sitting on your lap. I figure after all those years of sitting on mine, you owe me."
I didn't mind at all, even though the heat from her body was making me even warmer. The bumpy movements of the bus was causing mum's ass to rock against my crotch. I tried not to think about the sexual nature of it but I couldn't stop. I could feel the swell begin in my pants and I knew Mum would notice it any moment. She appeared to be concentrating on the passing scenery so I tried to wriggle myself out of this sticky situation. My movements only made things worse as I felt my erection slide right between the cheeks of her ass.
I'm not sure if Mum was uncomfortable with the situation or whether her dress was the problem, but she lifted her ass momentarily and flared her dress at the back. She settled back down, with my erection finding the groove of her ass straight away. Her movements had caused her dress to ride up at the front. My eyes were glued to her legs. They looked so inviting. I wanted to run my hands up them, but I knew it was inappropriate. I decided just to rest my hand midway along her bare thigh. I could get away with this innocently enough. Her skin was hot to the touch, but so smooth and soft. I nearly came right then. She didn't pull away which calmed my nerves a little. I slowly slid my hand down her leg until I reached her knee, then slid it back up. It was more affectionate than sexy, but I went a little higher than I had been previously. I repeated this a couple of times until my hand was at the top of her thigh. The hem of her dress was pulled right up to her panty line and I could feel the elastic of it through the cotton dress. Mum's eyes were closed but I could tell she wasn't sleeping. The movement of her ass on my crotch had changed from the random bounce of the bus to a regular back and forth motion. She knew what was going on and for some reason she wasn't stopping me. So I did what any horny young boy would do... I kept pushing my luck.
I placed my left hand on mum's waist and slipped my right hand under her skirt, resting it on her stomach. I gently traced with my index finger from her belly button down to the top of her panties. I followed the elastic around to her hip and along the side seam. Again I followed the elastic around the seam of the leg, this time ever so slowly edging closer to her pussy. I could feel the heat emanating from between her legs. Her underwear was damp from a mixture of sweat and excitement. I ran my fingers along the valley in her knickers caused by her swollen lips. She squirmed, parting her legs and giving me more room. My hand edged inside the leg of her panties. Her soft pubic hair was dry on her mound, but as my fingers pressed into her folds it was wet and sticky. I separated her lips and slid my finger inside her hot pussy. She leant the back of her head against my neck and shoulder, while I stroked her inner walls. I withdrew and took her engorged clit between my fingers. Rubbing it and pinching it gently, she let out a soft moan into my ear. I took this as a sign that she was enjoying my attention. I pulled mum's body back against me and then reached around between her legs to undo my fly. Mum, pushed my hand away and I knocked the old man sitting next to us. He stirred from his sleep, slowly opening his eyes. The first thing he saw was mum's parted legs with my hand inside her panties. He watched intently as mum reached down and undid my shorts revealing my hard cock. It sprang up between her legs and she grasped it around the base. Mom guided the throbbing head towards her pussy and with her juices and my precum to lubricate, she massaged her clit with the head of my dick. I moved my hand to cup her breast and could feel her hardened nipples through the material. She managed to keep her moans to a soft whisper in my ear.
"Baby, you feel so good. Do you want to be inside mummy?"
I thrust my hips upwards and she arched her back, guiding the tip of my stiff cock inside her. With one movement she lifted and slide right down my shaft so that I was completely inside her. The man next to us watched in amazement while he rubbed himself through his pants. This turned mum on even more. She was still cautious not to alert the whole bus to our actions, but she ground her ass against me like she hadn't had sex for years. One of her hands rubbed at her clit, while the other gripped my leg to give her something to push against. Just as I was getting close to orgasm she dug her nails into my flesh and shuddered. A groan that was slightly too load escaped her lips as she threw back her head.
"Cum inside your mummy, honey"
Her pussy tightened around my cock giving me the greatest sensation I have ever experienced. I felt the rush of sperm flow though me and inseminate my mother. I continued thrusting through my hot cum, and felt it combine with mum's juices and pump out over my balls with each deep push inside her. Mum's moan was enough to make the people a few rows either side of us look. They must have known by our closed eyes and flushed faces exactly what was happening. It was then that we came back to reality. Mum slipped her panties off of her legs and handed them to the old man sitting next to us. With a wink to him, she pressed the bell, straightened her dress and moved to the door. I quickly put my cock away zipped my shorts and headed towards mum. I could see the cum running down her leg but she didn't seem bothered. She just turned to me and said "We'd better get home and unpack the shopping before your father gets in. I might need a shower!" And with that we exited the bus to walk the rest of the way.