Shounen ga Otona ni Natta Natsu. Ryuki Kirishima is a young boy who lives with his older sister, Reiko, after both their parents died tragically in a car accident. One summer day, Ryuki and his friends get together to watch adult videos for entertainment. Although Ryuki is usually not interested in such content, But when he sees a porn video featuring Kiriru, a popular new porn actress. Ryuki becomes very horny. Then when she watches Kiriru's porn video alone somewhere in the middle of the forest Kiriru appears in front of her for real to invite her to have sex.