Ore no Imouto ga Saikou no Okazudatta

My very own little sister caught me masturbating to a little sister Eroge game, then my cool, calm and collected little sister suddenly decided to help me masturbate… She even made my friends masturbate, and somehow got the most beautiful girl in school involved!? Will i be able to get a girlfriend if i can only cum to my little sister!? and also… Why is she still watching me masturbate!?