Someone asked me that, and it's interesting, so
In the connected universe (my sun, the tale of the lines, and a few future books share a universe. )
Ace people have a specific line pattern on top of the normal one.
Aro people will have a different lime pattern, and will have a small purple patch in their eye.
Aroace people don't have lines at all, but will not show signs of lacking a soulmate, since they are marked by Akira on their leg, meaning they're approved of living.
Ace and aro people who are repulsed by relationships will usually end up as either forest leaders or gardeners, as they are more connected to Siler than to Akira.
(I'll explain more about the gods later)
And yes, there will be a few of those characters in the books, one of them will also be VERY important for the entire storyline.