"I promised I'd do anything if you got perfect scores on your test, right?" For three days, the arrogant sister who mocked her younger brother finds the power balance completely reversed. With their parents away, I'd been aroused every day by my sister's defenseless breasts and big ass, so I devised a plan: force her into lewd cosplay and make her climax. The more she resists and snaps at the nipple-exposing outfit, the more my sexual harassment training intensifies. Ordering her to suck me off, I lose control watching her moan in pleasure, driving into her with relentless doggystyle thrusts. Gradually, my once-proud sister becomes obedient and horny, until I make her understand through repeated orgasms and creampie after creampie.