I was just finishing with the popcorn when my sister came into the kitchen. She had changed and put on one of those spaghetti strap tank top shirts as well as a pair of boxers. This was her comfort wear I guess. But it sure did show off her full boobs. Now, I'm not "into" my sister in any perverted way, but when anyone with a body like her's walks into a room, you would still look.
Anyway, she came up and grabbed the bowl of popcorn off the table.
"I'm going to play the movie", she said.
When she said it, she pretty much sprayed the word play. I got a face full of spit, some in my eye as well. I was used to this and didn't pay it much mind. However, as I followed her out of the kitchen, I felt a wave of fatigue pass through my body. I plopped on the couch and began to watch the opening credits of the movie, passing the bowl of popcorn between my sister and me.
As the movie went on, for some reason, I could not get over how big my sis's boobs looked in that tank. I kept thinking to myself, what if they were bigger? I began to imagine what she might look like if they were.
My train of thought was interrupted when I saw my sister move out of the corner of my eye. Looking over, I saw she was adjusting the straps on her tank. However, it was her boobs that drew my attention. I could swear they looked larger than the last time I saw them.
As I continued to look at them, I thought I must be imagining still. It look as though they were still getting bigger. I thought I was crazy until my sister looked down. She let out a gasp as she cupped her expanding tits with her hands. I must have been sitting there open jawed. She immediately got up and ran to her room.
I could not believe what had just happened. I had imagined my sister getting bustier, and moments later, it actually happened. That powder of my Grandpa's must have given me some kind of mental power. How else could it be explained. I decided that further testing was required.