The series 'Chii-chan Kaihatsu Nikki' documents the complete sexual corruption and mental breakdown of the innocent student Chiharu. Under the sadistic tutelage of the mysterious Onija, she is systematically stripped of her will and remolded into a depraved fucktoy. The 'development diary' chronicles every debased step of her transformation, from her first forced encounter to her eventual mindless submission. Viewers watch as she is subjected to a relentless barrage of humiliating training, including public exposure, group sex, and a variety of intense BDSM scenarios, all designed to shatter her psyche and awaken a bottomless well of perversion. Her body and mind are treated as a canvas for Onija's lewd experiments, culminating in her becoming a mindless, drooling pet who exists only to have her holes used and filled with cum.