I stay at home and play erotic games on my smartphone all the time, but I've got my eye on my sister's big tits, and I've Itsuka wanted to do what I do in those games with her. One day, my parents are going on a trip to celebrate their wedding anniversary. Taking advantage of my sister's gentle nature, I see this as my chance to do what I want to her. At first, she doesn't want to do it, but she seems to like what feels good, and even though she's a bit embarrassed, she gradually starts to do what I ask her to do...