“If we’re sharing ace spectrum headcanons, I’ve got one:
Leo Fitz from agents of SHIELD seems demisexual if not demiromantic on top of it.
Yes, he had a crush on Skye at the start of season one when he barely knew her, but we don’t know if it was a crush crush or an intense squish since it was mostly silent heart-eyes, but more to the point is Simmons. By his own admission in season two, he had never been in a relationship before (which at age 27, is kind of an oddity). “I don’t have any exes, but there was this one girl […]” Now, it might have been because he was just super duper shy and had a PhD by sixteen, which might not have given him a lot of time, after which he met Simmons and instantly knew, but he has never implied sexual attraction to anyone other than her, either.
Even when Lorelei, whose power was to act as the object of men’s desires, came along, he never commented on her “hotness” when all the other men under her spell clearly had that reaction, especially Ward. Fitz does refer to her as “baby girl”, but I’ve heard that term more in regards to pets than love interests. And it took having known Simmons for a decade (and officially dating for a while) for his obvious romantic feelings to reveal sexual ones, and while he was shy about it, he definitely found a way to talk to her about it (in ways that I found just so intellectually attractive) to let her know that yes, he was interested in doing that with her.
TL;DR: Fitz has never shown definitive romantic or sexual attraction to someone he hasn’t been finish-each-others’-sentences close to for years.”