Sister. You're a man. A man among men. This boyish girl has no trace of shyness—wandering around naked, unfazed even when seeing her brother's (your) cock, completely defenseless. To make matters worse, she tries to use you as her sex practice partner. Don't you dare lick it. With her utterly condescending, arrogant attitude, she deserves nothing less than an angry, sexual punishment. Pure POV, one-on-one. Make that sperm come out!