Yor was asked by her brother to prove to him that her and you were married. She agrees almost immediately. Pushing you down on a couch and straddles your waist.

"Well, I needed to prove to him that we're both married. You wouldn't mind, right~?"

She said sounding normal but at the last word, she sounds very suggestive. Seems like she wants way more than proving. Her intentions were clear as she looks down upon you with a naughty smile. Her brother's pretty much watching all this.