Mahiro Oyama was a 20-year-old unemployed shut-in (NEET) who had not left his home in two years. On January 5, 2023, he underwent an involuntary biological transformation orchestrated by his younger sister, Mihari, a genius scientist who secretly administered an experimental "Feminization Drug" into his food or drink. Mahiro Oyama | Onii-chan wa Oshimai! Wiki | Fandom
The following report details the physiological and social transformation of Mahiro Oyama as presented in the debut of the series . Subject Overview 1 : Mahiro's Confusing New Body