Actually ...

"I want us to pretend we're dating."

 Ruby had just left, and Sarah was taking a slow sip of her coffee, when suddenly Billy uttered those astonishing words. How could Sarah not be surprised?!

 "Haha... what are you doing?"

 "Actually it's a secret. But I had to reveal it to you." Billy kept his face serious, as serious as he said.

 Sarah was getting more and more clueless. "Secret? This pretend dating invitation, you mean secret?"

 "No." Billy shook his head. "But the reason why I asked you to pretend to be dating."

 Sarah rolled her eyes. "Come on, Billy. I'm not that unsavory woman to pretend to be dating an ordinary guy like you. You don't have to say the reason and I know you really want to feel like you're dating an extraordinary girl like me, right?"