Totsuon!: Totsuzen Onnanonko ni Natta no de, Ore no Oppai Monde Mimasen ka?

Sakio's world shatters when he awakens to find himself inexplicably transformed into a girl. As confusion turns to panic, he seeks answers from his best friend, but their attempts to understand his new form led to an unexpected and arousing encounter. Now a girl, Sakio must desperately conceal his secret and fight to retain any semblance of his old life, as his stepbrother's inappropriate and unwelcoming interest grows. (Source: Coolmic)