Reuploading it as I changed some details - namely the girl design. I wouldn't change guy design though, it's a common appearence and my favourite hair colour so yeah
So here is the story of what's happening in this animation:

The guy was searching in Internet for a cute dress which would totally suit his favourite anime waifu, and then suddenly decided to buy it on a whim. (yes, sertainly not for himself or anything, haha. Absolutely not! Just for an aestetics! Honest truth!) Which leads to an instant delivery and a few magical adjustments to make the dress fit.
Then his childhood friend (girl) walks in to be very surprised by the change. They are very good friends and best bros, always watching anime together, playing video games and talking about cute girls. So his friend appreciate change a lot! XD (it's a tempororal one, though. Lasts 24 hours only). He doesn't know what triggered transformation though, so some time later he order another cute dress from the same site (which leads to the same results). It'll took him a while to figure it out^^ So a lot of different cute dresses to change into (for me to animate)