My timid and serious sister-in-law and I, who have a strong sense of self-confidence, don't get along very well. To begin with, I hate my sister-in-law because she looks so neat and tidy that both my parents and others think she's reliable. So if my sister-in-law tries to act like a big sister, I punish her by slapping her! I also train her to be a naughty lesbian and make her my sex slave who obeys me completely! Not satisfied with that, I also get my boyfriend and my sister-in-law's boyfriend involved in a swap! At first, the timid sister-in-law couple were confused and teary-eyed, but they couldn't resist the waves of pleasure and became more and more lewd... This is the true nature of serious sisters-in-law. I hate my sister-in-law, but I got the best toy, so I don't think I'll get bored of her anytime soon.