Aoi Hazuki, a busty subject with 100cm I-cup breasts, participates as a test subject in an experiment conducted by Japan's only official paizuri research institute, the All-Japan Paizuri Research Institute. Standing in a lab dressed in her uniform, a male researcher slowly fondles her massive breasts from behind, meticulously studying their texture and elasticity. Even through her clothes, the softness and firmness of her tits are evident, gradually turning Aoi on. While observing her reactions, the researcher makes her masturbate, capturing intense footage of her climaxing repeatedly through vigorous tit stimulation. Next, her uniform is removed for closer examination. Oil is drizzled over her tits as they're pressed against an acrylic board, visually recording their glossy transformation. She then undergoes strapon titty-fuck training, brought to orgasm using the dildo. After passing the strapon paizuri test, Aoi performs real titty-fucking on the researcher's cock. She fully erects him with a saliva-drenched blowjob before demonstrating various titty-fuck techniques. The researchers can't hold back, erupting in massive cumshot sessions. Wearing a sheer school swimsuit, Aoi undergoes a body-washing experiment with foamy soap. As she's scrubbed, her tits are groped and used for soapy titty-fucks. In the final experiment, all researchers surround her, relentlessly groping her huge breasts. She's continuously assaulted with vibrators, dildos, and anal beads, moaning loudly and orgasming repeatedly. She then deepthroats each researcher's cock, performing sequential titty-fucks in an assembly line. Amidst cumshot play, she's pounded in intense big-tit bouncing sex by well-endowed researchers, screaming in ecstasy as she squirts repeatedly. Even after multiple orgasms, she's relentlessly re-fucked, drenched across her massive breasts with the researchers' copious loads.