While mom and dad are away on a trip to the local hot springs, Mai, 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 entrance, the bedroom, the bathroom, and more, and cums all over the place! "Big brother is amazing! You've produced so much milk, you can do more, right?!" *There are no performers under the age of 18 in this work.