After losing your virginity to your girlfriend, and falling asleep, she gets a text message from your big brother in the next room over, who used to be an old sex friend of hers. While you're still in bed, she heads over for some real fun...
"Please... delete the image you took!" One day, you happen to notice Ui and her boyfriend entering a love hotel. You promptly take a photo of them, and send a letter to Ui. "If you don't want me to expose your dirty little secret, do whatever I say."