My girlfriend won't let me have sex unless I create the right mood, so I splurged and invited her on a hot spring trip, but to make it harder for me to have sex, she brought her sister along, and I thought I was doomed. Or so I thought, but her sister, Nana, is secretly a nymphomaniac, and contrary to her innocent demeanor, she seduces me as soon as we arrive at the inn. "Touching you with your hands isn't cheating, you know?" Despite feeling guilty, I gave in to her sister's devilish seduction...