Aimai na Ore to Kachiki na Imouto no Kankei

My little sister Saya would hide in my room and masturbate -- and I kept feigning ignorance. One night, while the two of us were alone in the house, I heard my sister say sadly, "Big Brother..." When I heard my little sister, who was usually so strong-willed, say those words, I opened a door I never should have... Am I going to love my little sister, or break her?