Today is the first day I went to my girlfriend's house. She lives with her older sister Katou, she is a nurse, often working night shifts. Whenever she is tired, Katou often falls asleep on the sofa. She also wears very loose clothes that expose her big breasts to my eyes. I have always tried to restrain myself, but when my girlfriend had to leave urgently, I couldn't stop myself anymore. I unconsciously approached her, my hand had been placed on her big breasts without me knowing. While fondling these big breasts, Katou showed no signs of waking up. So I became more and more daring. Burying my face in these big breasts, sucking them, rubbing my dick against them, and Katou still didn't wake up! At this point, I could rest assured and proceed to insert my dick into her wet pussy...