The Futanari Train -

Futanari media typically centers on "gynomorph" characters—individuals with an overall feminine appearance and biology but with dual genitalia.

The term (ふたなり), literally meaning "dual form" or "to be of two kinds," has roots in Japanese history as a term for hermaphroditism and androgyny. The Futanari Train

: Common narrative drivers include magical transformations, scientific experiments, or "curses" that alter a character's biological sex. The Futanari Train