As for the story, I think it would be fun if the model is my younger college sister who I am really mean to. The video begins with her complaining that I always pick on her and make fun of her being smaller and weaker than me, and that I don't deserve to be bigger and stronger.
Then, I shrink, and I am the same height as her. The conversation between me and my sister continues as if nothing at all happened, but all of a sudden from my perspective the conversation has taken a turn where instead of complaining, my sister is actually commenting on how nice it is to have always been the same height as her brother (me), and how she thinks that has really made us closer as siblings. From my perspective, when I blacked out, its like all of reality changed at once, and my sister can't remember me ever being taller. When I tell her that I did used to be taller, she calls me silly and says "You wish! You know you've always been on the shorter side for a guy and me on the taller side for a girl! Stop dreaming haha". At this stage, she might even say something along the lines of "It really is a good thing that neither of us is the taller one, because I think we would be pretty mean to the other if so."
Then, after that stage, another shrinking happens, and I am eye level with her shoulders. are you okay? Or are you still dreaming about being as tall as me? Haha." I act surprised and she says "Oh come on seriously? Are you still playing around? You know you've always been shorter than me, ever since high school. I mean honestly I always felt kind of bad for you, what with me being so tall and you being so short." And it kind of continues on in this way of light height humiliation for a little while, her telling me that she pities me and that I should be happy that at least I'm still cute for a guy so I'll probably be able to find a girlfriend as long as she's also short.
I shrink gain after she says this and when I awake I am eye level with her tits. I respond by saying "Hey that's mean, I can get any girl I like!" and she responds by pointing out that I am level with her chest and there's probably no girl on earth that would be okay with that. Then she starts to make fun of me for how much I stare at her boobs while I'm at this height and how pitiful of an "older" brother I am. She talks about how she can't believe how very much taller she is and how she tells people at school that I'm actually her younger brother. She then offers to smoosh her boobs up to my face since its probably the only ones I'll ever get close to. This stage ends by me saying something along the lines of "Why am I shrinking!" which she just gets kind of annoyed with at this point saying "You're not shrinking, you've just always been this puny! Look, lets go back to back, I'll show you." Then she turns around and puts her back up close to the camera, and I shrink one last time.
This time when I wake up, I am eye level with her waist/hips/ass and she turns back around as says "See!! You've always been a little dwarfy shrimp. Its so sad, but you are soooo cute!" At this stage, I think my sister goes from being aggressive to actually kind of affectionate - when I'm this small, she sees me as kind of her plaything, since she's always been so so much taller than me - she tells me this too, she says things like "You know, I loved growing taller than you in just the 6th grade! It made me feel so big and powerful. And now that I'm soooo much taller than you I just can't help but want to be close to you. I know you love it too, since no one else will ever want to be with you." At this point she gets really close to me and starts doing a lot of body comparisons. "Look! My hips are even wider than your shoulders! And my legs reach up to your shoulders!" The closer she is to the camera in this section, the better. The more body comparisons in this section the better. I'd love for her to comment on just how much bigger she is than me in every way - how big her hands are, how thick her legs are compared to my torso, how a grumble of her tummy probably sounds so loud to me, how scary it must be for me to have to look so so far up at her. How she is so glad that she is not as small as me, even if I am cute.
I think the video then ends by her turning around and puttying her ass right in to my face and going on and on about how she knows how much I love to stare at it, and that she's so glad I'm her smaller older brother and that she's glad that my delusions of being taller aren't real so that she can have someone to appreciate her ass and huge body as much as I do.