You decide to go to your sister's room. The logic was simple, it was the one closest to you and you just wanted to do a small test run with your size. You definitely weren't planning to do something other than sneak in under the door and watch your sister sleep in, then come back and wait until you got your height back.
You take your time walking through your room until your closed door, noticing how rough the carpet feels against your naked body, and then overcoming your first real challenge as you crawl under your door towards the hall successfully. You smiled once you made it through, feeling like you were doing some sort of mini workout in your own home having to walk and crawl like that, if you got creative you could easily add other exercises like climbing or jumping through things. This helped you focus more on the current experience than on the project to sneak into Bea's room, as you clearly needed to do some research first to do that safely.
The hall doesn't have a carpet so it feels quite cold to you, but you only last there about half a minute as you make it to your sister's door and go back to crawling. For some reason you have a harder time with this door, and as you look at your side you can see why. The door has some slight, barely noticeable inclination, but for you this tiny misadjustment could apparently make quite a bit of difference.
Your eyes adjust to the darkness as you internally celebrate the succesful test. Sneaking in past doors? Easy. At least in your own home. No noticeable signs of fatigue or any of those other nasty side effects mentioned on the bottle's printed text either which is excellent news, and based on what you felt since the pill did its magic, no other weird effects whatsoever, just same old you at one inch tall and naked.
Taking a look around you focus on the bed and the big lump of your sister, Rebecca, sleeping peacefully under the covers. She is one year younger than you and like you fully focused on the college life. You are on friendly terms with her but due to how different your interests and schedules are you aren't that close to her anymore, in fact most days you barely greet each other. She is more extroverted and outgoing than you, and in a way more prudish or conservative in some things. You certainly don't believe she would be able to scour through the corners of the internet to find a pill capable of shrinking people, and you don't believe she would be interested in any out of the ordinary fetishes like the uneasy thing you have going with Bea.
A movement on the bed cuts your thoughts and while asleep, Rebecca turns on the bed and pulls the covers along with it, letting part of a leg and a foot exposed. Watching what just happened starts taking your mind to other directions, directions you have never considered before because, well, she is your sister. You just don't involve her or your mother when thinking about your fetishes.
But with your tiny size, looking at her exposed sole as if it was destiny talking you gain a new perspective and start seeing Rebecca literally in another dimension. The inevitable questions pop up, how would she react if she saw you? Would she be kind? Would she .. like you at your new size? Would you find a ... secret mean streak like the one Bea shows when she bullies you? Even if you never thought of your sister like that you have definitely seen the fantasy stories out there put out by fellow anonymous fetishists that do involve family, and recalling some of those scenarios make you start seeing your sister in a new light.
The uncertainty of her behavior also makes you second guess yourself, what exactly do you expect or want Bea to do with you? Sure, she likes teasing you but is she truly doing it because she likes it or just enjoying making fun of you? would she think you're crazy? would she.. get rid of you if she finds out about your tiny self sneaking on her? The doubts creeping in make a crack in your expected dream scenario, you don't even know if sneaking into her apartment like you think is actually possible. With the image of Bea as the target of your obsession becoming a bit blurry the idea of a safer target starts sounding more appealing.
Whatever you decide, you know you probably don't have a lot of time. All you know is that if you are giving in into this the best thing you can do is take a closer look. With this darkness you can't really see any details on her foot from your position, and you don't even recall if Rebecca has nice feet or not, you somehow never noticed. If they weren't good you could move on, but then again, was it Bea's feet or her attitude or something else? So many doubts. You could climb the bed and accept her generous offer, or take a safer route exploring and finding some footwear on the floor, although at first glance you don't see anything. Or you could just focus on the original plan and not making something you could regret very easily.
What happens next?