Start the story with a young male protagonist that is shy and lonely. Describe in detail their sudden and very pleasurable transformation into a stunningly beautiful and horny futanari. The protagonist will grow a huge pair of breasts that produce large quantities of milk when stimulated. Their male genitals will expand disproportionately into a massive meaty cock. A set of feminine folds also develop that are only visible when the protagonist bends over, otherwise her pussy is hidden behind a set of huge bloated balls that produce surprising amounts of semen upon orgasm. After this transformation, switch to using she or her pronouns when referring to the protagonist. There doesn't need to be an explanation for this transformation.