There are a lot of nuances to the asexual spectrum and aromantic spectrum -- they can overlap in a myriad of ways, and sometimes be informed by neurodivergence and/or trauma, all of which is valid.
For writers wanting to add ace and/or aro rep into your books, it's worth talking to ace and aro people, and those whose orientations sit on both spectrums, as having this perspective can really help.
Honestly, I think it's just way more interesting to have this kind of rep, too, because we aces and aros can flip and subvert story expectations and narratives, no matter what genre this rep is in.
What happens if you take sex (but not necessarily romance) totally off the table as a motivator for a male character who is very "macho" or perceived as that? How does that change/subvert expectations? What vulnerabilities does this add, and how might it complicate his storyline?
What happens to the dynamics of a situation when one person is very comfortable having sex with all genders but only romantically attracted to certain ones, or vice versa, so they could fall in love with someone they aren't sexually attracted to, or be sexually attracted to someone they won't fall in love with?
What happens if you're writing spice and a character is fine with sex but just never falls in love; what would changing a subplot or main plot into a Strangers-to-BFFs-With-Benefits do, if you wanted to look at ways to open things up and explore queered relationship structures?
How does jealousy manifest in these relationships, if it does, and how do you navigate that?
In an SFF situation - how would any of the above impact the dynamics of a group of characters, with forced proximity of a quest or castle or space station or something they can't leave so they're all stuck with each other? It doesn't have to make something "boring" if spice isn't added... It can create opportunities for growth, new situations, conflict, and resolution to issues.
In horror, sex averse MMCs basically take SA off the table totally as a means to shock or disturb the audience, and mean the writer has to actually work with that and create more interesting antagonist characters with deeper motivations. It also changes the dynamic when someone is literally only interested in your body from an anatomical point of view, and if you start coming onto them, they freak out and have no idea how to handle that situation, which can even flip the power dynamics. (See also: my touch-starved cannibal in The Crows).
You can also use it for deepening emotional bonds in romances of all types, as demisexuals and demiromantics are perfect for the slowburn trope. Explicitly exploring demi orientations gives additional things to develop and talk about, too; what will help them create the emotional bond the demi character requires in order to feel sexual and/or romantic attraction to the other person?
Note: if the person is demi and the emotional bond isn't formed, the only-one-bed trope won't work. BUT you can use that to create more angst for Character B if Character A is demi, and then reprise it later once the demi character is fully into them...
Anyway - almost everything I write has ace, aro, or both spectrums rep in it, not necessarily both, and I would love more people to know that!
Ace and Aro rep can be found in:
The Crows
Thirteenth
The Day We Ate Grandad
The Sussex Fretsaw Massacre (& Other Stories)
(all of these have unlabelled but very obvious and on-page ace/aro spec rep)
The Reluctant Husband (aesthetic attraction is present, but the MMC is lowkey aro and grey-ace, unlabelled as it is set in 1938)
Birds of a Feather (contemporary romcom with aro-spectrum and sex averse ace MMC, he doesn't label himself but microlabels are speculated)
Yelen & Yelena - aro only, Queer Dark Gothic Fantasy
My stuff for those interested:
janainaart
stormborns
germansingergirl
jbbartram-illu
kianamaiart
izzy806
snowghoul