It might be about self - discovery too. Through the encounter in the story, the narrator could learn more about their own prejudices or open - mindedness. For example, if they initially had some narrow - minded views but through getting to know a shemale, they changed and grew as a person. Also, the theme of friendship could be there if the story involves building a relationship with a shemale.
One possible main theme could be acceptance. Discovering and coming to terms with the existence and uniqueness of shemales.
The main theme could be about breaking barriers. In many societies, shemales face various barriers such as social stigma and discrimination. 'My First Shemale Story' could be about the narrator's journey in breaking those mental and social barriers, realizing that shemales are just like any other people with their own hopes, fears, and dreams. It could be a story that challenges the status quo and promotes equality.