Looking for a one-shot manga about a loli and a hired brother

I am looking for a manga, but I can't remember if it was a one-shot or just one page

What I remember is a little girl having fun with her big brother (in the festival I think) before they were interrupted by the alarm clock on his phone. His face went from happy enjoying his time to not caring while saying something along those lines "your time is up. Thanks for choosing me to be your big brother"

I don't even know anyone will find it