My Older Sister is a Villainess

My older sister is a villainous lady. My sister gets her engagement broken off at the school's graduation party. It's not really a problem in itself, but the issue is that my sister ends up being sent to a convent after that. I decided to do my best to somehow avoid her being sent to the convent. I wrote this to submit it to the Naro Radio Grand Prize. [8/1 I've inserted the fan art I received at the end]