On a midsummer day, Yuzuru visits his brother's house. With the air conditioning broken and unable to bear the heat, he is seduced by his brother's wife, Unpai, who has changed into a micro swimsuit. As the heat makes her drink more, she loses control and approaches him in a tiny bikini. Unable to resist his sister-in-law's lewd swimsuit and nympho big ass, he ends up fucking her sweatily over and over again...