To begin with, both demi and graysexual people under the umbrella term asexual. To put it plainly, people who identify as demisexual are people who may feel sexual attraction after a strong romantic bond is formed.
When I was 16 or 17, just starting to realise that I was trans (though FAR from accepting it), I was also in the early stages of identifying as asexual. I always felt like my attraction to girls was different than people around me. Obviously, I later realised it’s partly because it was gay attraction and not straight attraction, but at that point I figured that the sexual component was missing for me.
I started college and along with that came new people, new stories, new ideas. Suddenly I had a friend who was thinking about transitioning, exchange students who didn’t fall into the binary segregation and even a gay couple in their fifties giving us a talk about gender and sex dynamics. But this isn’t when everything changed, it changed when a girl with dimples and superhero t-shirts told me she liked me.