Halloween Romp/Pull her skirt to the ground
You weren't walking very fast since your sister was distracted by her phone. Very carefully you pull back on her suspenders and just as you hoped she slowed down to a crawl, her steps much smaller than they just were. Reaching forward to grad the other end of her suspenders, now having four points to pull at her skirt.
With your heart pounding in your chest you ever so gradually pull the suspenders down. The waistline of her skirt peeled down a bit, just enough to see the top of her panties underneath, and Angel continued to remain unaware of what you were up to. Emboldened a little you start tugging a little harder and at different angles, matching the tugs with her steps so she wouldn't notice her skirt inching its way down her hips.
It felt like ages but you finally got the waistline of her skirt to the widest part of her hips. This was the trickiest part; you had to pull it down fast enough and at the right moment so her legs wouldn't get caught in it. You take a deep breath, look around just to confirm you're still alone, and carefully watch your sister's flawless legs waiting for the right moment.
There!
With a swift yank you pulled her skirt off her hips, down her legs, and to the sidewalk so fast you watch as she steps out of her clothing without breaking stride.
How well did it go?