While mom and dad are away on a trip to the local hot springs, Chiharu, an active little sister, plays naughty pranks on her beloved big brother. She has sex with him all day long, without a break, in his room, the kitchen, the hallway, the bedroom, the bathroom, and more, and cums all over the place! "Big brother, you're amazing! You've released so much white stuff! But you can do more, right?!"