My little sister Yui. She's cute and has a serious personality. But she's actually very interested in sex!? Because she has sex with me every day, she barely passes her exams. If she keeps going like this, she'll fail. We're banned from having sex for two weeks and study hard together! We somehow managed to pass the exam, and today we're alone together for the first time in a while. As soon as we got into the love hotel, we started kissing! Both of us were at the peak of our sexual desires and immediately wanted each other! Even though it was my ovulation day, we came inside her many times! She said, "I'll kill you if you don't cum 10 times!" She kept tempting me, and I wondered what would happen to me if I continued like this!?