To repay her younger brother's debt, Hikaru Nagi, a busty J-cup sister, is forced into three days of confinement and complete servitude under a wealthy older man. Whenever he gets aroused, he demands she squeeze his cock between her massive breasts, leading to an intense climax where he absolutely must cum between her tits. Her divine breasts are groped, sucked, licked, and used for relentless titty fucks, subjecting her to thorough breast training. Though initially disgusted, aphrodisiacs and lubricants heighten her sensitivity, making her wet instantly from breast play, taming her into an ultra-sensitive, depraved slut. She repeatedly performs titty fucks, and even after cumming, his cock stays hard, thrusting with unstoppable stamina as she drowns in pleasure. Using her brother's debt as an excuse, even after the contract ends, she craves his cock and shockingly submits herself to become his permanent tit slave.