Oxytocin

"Andrew we can't do this," I pleaded with him, my best friend's brother, as he kissed my neck passionately.

"Don't worry," he replied and wrapped his arm around my waist, his fingers caressing my waist.

"Andrew please," I said pushing him off of me. "I promised her."

"Lea," he said wrapping his arm back around my waist. "I don't care what she thinks."

"I do," I said pulling his arm off and taking a step back. "She's my best friend and I can't do this to her. I promised her Andrew. I'm sorry."