When I called out to a man and woman who were acting like a couple at a resort, I found out they were actually brother and sister, and what's more, the sister was a slut who changed men all the time, and the brother was a shitty virgin! I proposed a game where the brother and sister play rock-paper-scissors, and if they don't get an erection when they see the sister naked, they'll win a prize! I also prepared a helper to avoid taking off clothes when they play naughty pranks such as deep kissing and hitting the vibrator. The brother and sister are used to seeing each other naked, so it's a piece of cake lol... but somehow the atmosphere is getting good as they go along, isn't it? They're brother and sister, right? The brother's erection is rock hard, isn't it? They're both conscious of each other, aren't they? Well, I don't care about sisters anymore, so let's become "man" and "woman"! Here is a documentary of a cheerful sister and a shy brother crossing the line!!